With Dijon mustard, thinly sliced ham, and creamy Gruyère, it seems the classic croque-monsieur was made for the casserole dish. If it's a brunch stunner you're after, or a dinner option with breakfast undertones, then this all-in-one baked take on the croque-monsieur should shoot to the top of your must-make list.
This dish can be assembled the day of, but it's actually best if everything up until the actual cooking is done the night before. This allows the flavors to meld together and gives the bread time to sop up the milk and eggs. When baked, the bread takes on the custardy texture of French toast and creates a firm-but-creamy base for the casserole.
Because this dish is so rich, it's topped with arugula dressed with lemon and olive oil just before serving. The bitter, peppery bite of arugula and acidic sharpness of lemon cut right through the rich saltiness, adding a bit of bright vibrancy.
As with anything simple and delicious, many variations on this sandwich exist: Add a fried egg on top and you have the croque-madame. The croque-Provençal sees the addition of tomatoes. Replace the ham with smoked salmon for croque-Norvégien. The croque-madame is especially popular; the name supposedly comes from the egg on top resembling an old-fashioned lady's hat. Take a cue from evolving interpretations of this sandwich to customize this dish with ingredients of your choice.
Baked Croque-Monsieur Casserole
Butter, for coating the baking dish
2 cups whole milk
7 large eggs
3/4 teaspoon freshly ground black pepper
1/4 teaspoon kosher salt
4 teaspoons Dijon mustard
12 ounces day-old crusty bread, cut into 10 (1/2-inch-thick) slices
1/4 cup chopped fresh chives
12 ounces thinly sliced ham
2 cups grated Gruyère cheese, divided
1 to 2 cups arugula
1 medium lemon, juiced
1 teaspoon olive oil
Generously coat a 9x13-inch baking dish with butter and set aside. Whisk the milk, eggs, pepper, and salt together in a large bowl. Spread the mustard on one side of each slice of bread. Place half of the bread slices Dijon-side up in the baking dish.
Spoon half of the egg mixture over the bread, making sure that each piece is fully covered. Sprinkle the chives over the bread and egg mixture. Place the ham slices over the bread in an even layer. Sprinkle with half of the Gruyère cheese. Layer with the remaining bread Dijon-side down. Pour over the remaining egg mixture. Sprinkle with the remaining cheese. Cover and refrigerate at least 30 minutes or overnight.
Arrange a rack in the middle of the oven and heat 350°F. Bake uncovered until the egg mixture is set and cheese is bubbly and lightly browned, 35 to 40 minutes. Let stand for 5 minutes.
Meanwhile, toss together the arugula, lemon juice, and olive oil in a small bowl and spread over the casserole immediately before serving.
- Storage: Leftovers can be stored in an airtight container in the refrigerator for up to 3 days.