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

Caramelized Mushroom Croque-Monsieurs

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
Prep Time 10 minutes
Cook Time 45 minutes
Total Time 55 minutes
Servings 6 sandwiches
Calories 747 kcal

Ingredients

Mornay Sauce

  • 1 ½  tablespoons unsalted butter
  • 1 ½ tablespoons all-purpose flour
  • 1 ½ cups whole milk
  • 1 bay leaf
  • ½ cup finely grated Parmesan

Assembly

  • 3 tablespoons unsalted butter room temperature
  • 8 ounces crimini or button mushrooms trimmed and sliced
  • 1 onion finely chopped
  • 12 ⅓” thick slices bread egg or white bread works best
  • 6-12 thin ham slices
  • 12 ounces Gruyère thinly sliced
  • 2 tablespoons grated Parmesan

Instructions

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.

Assembly

  1. Melt 1 tablespoon 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 tablespoons sauce on top, leaving ⅓” 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.