Caramelized Mushroom Croque-Monsieurs

These caramelized mushroom croque-monsieurs are fancy ham and cheese sandwiches with caramelized mushrooms and onions, and parmesan filled Mornay sauce. || Delicious Not Gorgeous

i was at a women in tech event a couple of weeks ago. my main takeaway was how incongruent it seemed to talk about confidence and empowerment and equality, and then be handed a giftcard for uber, a place notorious for its mistreatment of the women in its workforce.

aside from that blunder, the other thing that stuck with me was how relatable the content about confidence and unapologeticness was. if someone on the bus is taking up too much room, i shrink into myself or towards the side of the bus, even though they’re the one manspreading (or being oblivious). i come up with compromises when i suggest ideas, before any hint of feedback rolls in. sometimes i’m reluctant to be decisive, since i feel like it can come off too aggressive. i’ve downplayed my accomplishments, even to close friends, because i don’t want to seem like i’m bragging. i noticed all these little hints before, but now they appear blaring, and i’m trying to catch myself before i do one of these things, and resist the urge. man, it’s hard to undo a habit.

the above lessons could extend to these caramelized mushroom croque-monsieurs: they could be seen as just sandwiches, and that seems so reductive and weakening. especially when there’s double cheese duty from stretchy, funky (not all the way to funkytown but close) gruyere to the nutty, slightly golden parmesan that crisps into the prettiest lace pattern when it sticks to the plate. did i mention that there’s creaminess from a seriously quick mornay, complete with parmesan woven throughout? the ham is fair game for a usual sandwich, but the toothy mushrooms take it right back to saucy assemblage on crispy bread with cheese fricos status.

and if you want to elevate it even more, what about a croque-madame, which adds a fried egg on top? i personally find these caramelized mushroom croque-monsieurs plenty rich and hearty sans that runny yolk, but you do you.

1 year ago: Buttermilk Oatmeal Raisin Scones, Orange-Scented Almond Olive Oil Muffins
2 years ago: America’s Test Kitchen’s Clumpalicioius Almond Granola, Apricot Almond Amaretto Pound Cake
3 years ago: Thomas Keller’s Chocolate Chip Cookies

This cross-section of the caramelized mushroom croque-monsieur shows all the ham and mornay and melty cheese in all of its glory.

Caramelized Mushroom Croque-Monsieurs
Prep Time
10 mins
Cook Time
45 mins
Total Time
55 mins
The typical croque-monsieurs have ham, Gruyere and Mornay sauce, but these ones get fancy with some caramelized mushrooms.
Course: Brunch, Lunch, Main Course
Cuisine: French
Servings: 6 sandwiches
Calories: 747 kcal
Mornay Sauce
  • 1 1/2  T unsalted butter
  • 1 1/2 T all-purpose flour
  • 1 1/2 cups whole milk
  • 1 bay leaf
  • 1/2 cup finely grated Parmesan
  • 3 T unsalted butter room temperature
  • 8 oz crimini or button mushrooms trimmed and sliced
  • 1 onion finely chopped
  • 12 1/3” thick slices bread egg or white bread works best
  • 6-12 thin ham slices
  • 12 oz Gruyère thinly sliced
  • 2 T grated Parmesan
Mornay Sauce
  1. Melt the butter in medium saucepan over medium heat. Add the flour and stir until pale golden, about 2 minutes. Whisk in the milk, then the bay leaf. Increase heat to medium-high; whisk until it begins to boil. Reduce heat to medium; stir until sauce coats back of spoon, about 5 minutes. Remove from heat. Add the cheese and a pinch of nutmeg. Season with salt and pepper.
  1. Melt 1 T butter in large skillet over medium-high heat. Add the mushrooms and onion; cook until the mushrooms and onions are dark and caramelized, stirring occasionally.
  2. Spread the remaining butter over 1 side of each slice of bread. Place the bread, buttered side up, on a baking sheet. Broil until golden, watching closely and rotating halfway through, about 3 minutes. Cool. Turn 6 slices over; top with ham, sliced cheese and mushrooms/onions. Top with remaining bread, broiled side up. Spread 2 T sauce on top, leaving 1/3” plain border. Sprinkle with the Parmesan.
  3. Bake at 450F until cheese inside melts and cheese on top is golden, about 10 minutes. 

Recipe Notes

Adapted slightly from Marlena Spieler for Bon Appetit, March 2011.

Take a bite out of a caramelized mushroom croque-monsieur!

more carby french things

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almond cherry bostock

This herbed feta and mushroom confit crostini is perfect topped with a super runny egg yolk. #basil #feta #toast #mushroom

herbed feta and mushroom confit crostini

49 Replies to “Caramelized Mushroom Croque-Monsieurs”

  1. Holy cow, Heather! This looks divine! I love gruyere and melty cheese makes me swoon :). I do all those little “girl” things too–my main problem is that I apologize for EVERYTHING! Like, I apologize when I express a totally non-controversial opinion. Ugh! It sounds like a really interesting event you attended. Have a great week!

    1. cheese makes me very happy too (especially when there’s cheese samples from whole foods or costco). i think the apologies just come out (mine do anyways), and we don’t even think about them! maybe now you can catch yourself and try to do it a little less (:

  2. While exploring France in my 20s I probably devoured 100s of croque-monsieurs, yet I’ve never tried to make one on my own. I had no idea uber is notorious for mistreating women in it’s workforce. I’ve been working not apologizing for myself and being confident in my expertise. It’s easier said than done but I’ve come leaps and bounds from where I started. Croque-Madame’s are my favorite.

    1. they’re pretty easy! (not as easy as the usual grilled cheese, but i think the time/energy spent on these is worth). a couple of ex-uber employees have talked about their experiences within the past couple months, and it overall didn’t paint a happy picture. you can find some of the notable stories here and here.

  3. Manspreading…hilarious!! Everything you said about shrinking away and downplaying your accomplishments is so relatable. Do you think it’s a learned behavior or just innately a part of who we are? I could psychoanalyze the you know what out of that one…
    This sandwich tho! It sounds delicious. I’m a sucker for mushrooms…and cheese 😉

    1. i think it’s learned. so many women do it, and even if someone doesn’t explicitly tell you to do it, you see it and soak it up. also don’t love the idea of it being innate (i’d like to think that we have more control over ourselves but who knows), so i’m hoping it’s not.

  4. What a palatable recipe, Heather! It made me hungry! 🙂

    1. thanks, agness! 😊

  5. My mouth is watering that sandwich is so freaking beautiful! Ok, now I feel the need to apologize for being so forward. I can sooooo relate to your post. Why do we apologize for parts of ourselves that seem so natural? Nature vs. Nurture argument at its core.

    1. apparently i’ve been thinking about nature v nurture a lot, and didn’t even know about the term. guess it’s time for me to ditch my computer science and business classes and go to some psych ones instead!

  6. Mmmmm this sandwich looks like every guilty pleasure I can imagine!! Yum!!
    And as I age, the more unapologetic I get when it comes to how I feel or expressing myself. But then I probably get labeled as a bitch hahahaha. Oh well 😉

    1. i love being around unapologetic people, though! i think it’s refreshing and i admire how all in they are with their opinions.

  7. TALK ABOUT A CRAZY BLAST FROM THE PAST!!! I am French and I used to go to France ALL THE TIME – and as we all know as this point, these sandwiches are a MAIN STAY at all the cafes!!

    1. you used to go to france all the time?! jealous. i’m sure that croque-monsieurs are amazing in all the cafes, but if i were in france, i’d be camping out at all the patisseries and boulangeries instead of pounding the sandwiches lol.

  8. I need this sandwich, like, now. I mean, this is just heavenly – caramelized onions and a ton of cheese? Yes, please. Though, I love your suggestion of the runny egg, I agree that this is perfectly delicious by itself. You really can’t go wrong with a good sandwich, can ya? Cheers to a great week 🙂

    1. all the caramelized onions and cheese! come to think of it, this sounds like a mushroom-y french onion soup in sandwich form 😋

  9. I dislike that you went to that conference and had (probably) the highest of hopes of walking away with great information to get you going in a positive direction. But to leave feeling a bit perplexed about the message is disappointing. I know how it feels to downplay your accomplishments or to hold back from saying something in fear of how you’ll come off when that shouldn’t even be the case. It sucks so much, but you make a great point when you say it’s hard to break a habit. I think you (and I too) will be able to do it soon enough and be better in the long run for doing it. With that said, um bonjour monseiurs. That’s really the extent of my french, but if I could translate “get your deliciousness in my belly” i would, no question there =]

    1. i was actually surprised that the workshop was so relatable; i went in with fairly low expectations, and was there more for duty’s sake than actual interest. i was just taken aback a bit by the presence of the uber giftcards, which weren’t at all related to the consultants and managers who led the workshop. (oof, and even right in this comment, i was struggling with trying to explain what i meant without being apologetic or compromising about it).

  10. Mushrooms and cheese is such a heavenly combo, this sandwich sure makes me hungry! Hope your week turns out well, have a good one:)

    1. hope you’ve been having a great week, too!

  11. This makes my mouth water! All the stringy cheese!

    1. i think you meant, “ALL THE STRINGY CHEESE! 😍😍😍” (;

  12. This looks absolutely irresistible!

    1. thanks, pamela! 😄

  13. Hi Heather, this looks wonderful. I’m going to try this later once my kids are in bed. I hope they don’t wake up due to the lovely smell.

    1. if i woke up to the smell of these cooking, i’d go to the kitchen immediately and demand some 😂

  14. Oh my yum! I love croque-monsieurs and this one looks SO flavorful with the addition of the mushrooms. The mornay sauce is gorgeous too! The women in tech conference sounds interesting. I totally relate to what you were saying about confidence. I do a lot of those same things too out of habit, particularly finding the balance between downplaying my achievments vs. “bragging”. Thanks for sharing your insight!

    1. sauteed mushrooms make everything better! (and it makes it feel a little less rich because it’s not just ham, cheese, mornay, bread and more cheese).

  15. Probably a lot of women still feel guilty about being successful and have trouble owning it. A result of centuries of a certain kind of role ingrained into us?? Who knows! But it rings so true with so many of us. Love a good croque-Monsieur… oooo and with an egg on top it is just so decadent and absolutely sinful!!

    1. ugh i wish women didn’t feel guilty for being successful though! it makes about zero sense. anyways, these croque-monsieurs are 😋😋

  16. I’m going to make these for Hubby and I in the morning. I’ll let you know how I get on!

    1. sounds like an amazing way to start the day! (:

  17. I never really thought about how confidence and unapologeticness kind of go hand in hand. Although, unapologeticness can just go hand in hand with rudeness. 😉 Lol. But I totally understand downplaying things. I do the same exact thing! I wonder if it’s just a woman thing? Anyways, I am LOOOOVING these sandos! Croque monsieurs are absolutely delicious in their own right, but WITH caramelized ‘shrooms?! Be still my heart! I could devour a few dozen of these! Cheers, girl!

    1. i think there’s a difference between being truly sorry and saying sorry because that’s your instinctive answer, but i can definitely see unapologeticness crossing over into rude 😉 a few dozen of these?! i like your ambition 😊

  18. It’s so interesting to think about how a patriarchal system has affected us even if that effect seems subtle. Thanks for sharing your thoughts on that and for sharing this amazing looking sandwich.
    Take care,

    1. i think it’s interesting, too! the effect seems subtle, but i think trying to reverse it (even a little) could be empowering on an internal level.

  19. The croque-monsieur looks delish! I absolutely love anything cheese, especially melty cheese like gruyere! Anyway, I totally relate to downplaying my accomplishments; it is just something I do since I always think that I can/should do better. Sigh. Have a great weekend, Heather!

    1. i think it’s awesome to always striving to be better! but that doesn’t mean your accomplishments aren’t amazing (: also, yes to all the melty cheese 😋

  20. I’ve never made them at home but I need to!! Especially since they are so so good. Great job on this!

    1. yes make them at home!! worth the time and effort, even if you forgo the mushrooms (:

  21. Since its our fourth year running with this recipe as the star of our Oscar night menu, I thought it only fair I write a review. Once you’ve tried it you’ll never enjoy a Croque Monsieur without the fabulous mushroom duxelles again! Make the effort to hunt down French ham. You won’t be sorry. And, yes, it adapts nicely for panini makers. Just move all the ingredients INSIDE the slices of bread; never mind that this changes the name of the sandwich. This is America!! We are loyal to our choice of braided challah for the bread. You may also find you like our routine of serving it with a creamy, spicy roasted tomato basil soup with bits of lobster swimming in it. Best sandwich I’ve ever had. Period.

    1. ooh i love the idea of making it a panini! extra crispiness sounds like a good thing, and you can just add the mornay and more parm at the end anyways (:

  22. Such a good read. Being a woman in tech, I always downplayed myself but then I got into a company where men dominated and that’s usually okay but damn the way they did it – it was just degrading and wrong. After many years there, I was forced to grow some kahunas and it totally changed my attitude but it’s such a terrible way to do it but I guess I had to be in it to grow from it. This sandwhich screams comfort to me 🙂 I would definitely fry up an egg and plop it on top and damn the parm on top is to die for!

    1. ugh that sounds like such a bad environment to work in ): glad that it forced you to stand up for yourself more, though! also feel like it’s more likely that girls don’t feel adequate enough compared to guys, especially in tech. also: can everything have parm on top?! please and thank you.

  23. I have not had time for breakfast yet, and now I see this! Perfect for my lunch. Thanks for commenting on my blog while we were overseas. I really appreciate it 🙂

    1. perfect for breakfast or lunch! although maybe better for brunch, since brunch always feels a bit intense and rich (;

  24. This looks so fantastic and delicious.


    Pd: My cooking blog is in Spanish with google translator in many languages.

    1. thanks, olga! (:

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