Cool to room temperature. Strain through a fine-mesh sieve into a bowl and discard the tea bags and any scrambled egg bits that get caught in the sieve. Press out any liquid that might be held in the tea bags back into the custard. Stir in the Grand Marnier.
Adapted slightly from Melissa Clark.
This can be halved; I like halving it when I only have half a pint of heavy cream left in my fridge, or if my freezer is packed!
The Grand Marnier can be omitted if you want a non-alcoholic ice cream.