Perfect for a holiday brunch or a relaxed long weekend, this Croque Monsieur Breakfast Casserole comes together easily and delivers rich, savory flavor that will satisfy a crowd.
This egg-forward bake makes a great centerpiece for brunch. Light and creamy with a golden top and crisp edges, it offers the familiar comforts of a Croque Monsieur sandwich without the fuss of making pastry dough. Using day-old croissants gives the casserole a bread-pudding–like texture that soaks up the custard and melds with the savory fillings.
Inspired by the classic French ham-and-cheese sandwich, this casserole features chopped Black Forest ham, nutty Gruyère, salty Parmesan, Dijon mustard, and fresh thyme. The combination creates a bistro-ready flavor in a brunch-friendly format: tender inside, bubbly and browned on top.
Ingredients:
- Unsalted butter
- Day-old croissants
- Black Forest ham
- Gruyère cheese
- Large eggs
- Whole milk
- Whole milk Greek yogurt
- Kosher salt
- Freshly ground black pepper
- Garlic powder
- Dijon mustard
- Fresh thyme
- Parmesan cheese
Step-by-Step:
Step One: Prepare the Oven and Baking Dish
Place one oven rack in the middle and one near the top. Preheat the oven to 375°F (190°C). Grease a 9×13-inch baking dish with butter.
Step Two: Layer the Croissants, Ham, and Cheese
Tear the croissants into roughly 2-inch pieces and spread them in a single layer in the prepared dish. Scatter the chopped ham over the croissants and sprinkle with 1 cup of shredded Gruyère, distributing evenly.
Step Three: Make the Egg Mixture
In a medium bowl whisk together the melted (and cooled) butter, eggs, milk, Greek yogurt, kosher salt, black pepper, garlic powder, Dijon mustard, and the fresh thyme until smooth and uniform.
Step Four: Add Egg Mixture to Baking Dish
Carefully pour the custard over the croissant pieces, pressing lightly so the bread absorbs the mixture and sits evenly. Finish with the remaining 1/2 cup of Gruyère and sprinkle the Parmesan over the top.
Step Five: Bake
Place the casserole on the middle rack and bake for 30 minutes. Move it to the upper rack and continue baking 15–20 minutes more, or until the top is deep golden brown and the center is set when gently shaken.
Step Six: Cool and Serve
Let the casserole rest 10–15 minutes before cutting. Garnish with additional thyme leaves, slice into 8 squares, and serve warm.
Recipe FAQs:
Day-old croissants are ideal because they’re slightly dried and won’t become soggy. To quickly dry fresh croissants, leave them uncovered on the counter overnight. If you’re short on time, bake fresh croissants at 375°F for about 10 minutes until they are no longer soft, then use them in the recipe.
Yes. This is an excellent way to use leftover holiday ham—swap in 1 to 2 cups of diced cooked ham in place of deli-style Black Forest ham.
If you’re serving a larger brunch spread, cut the casserole into smaller pieces to stretch it to about 12 servings.
Enjoy this Croque Monsieur Breakfast Casserole for Easter, a holiday brunch, or any weekend gathering. Leave a comment after you try it!
Want more brunch-friendly recipes? Try these!
Mini Ham and Gruyère Quiches
Sausage McMuffin Egg Bake
Broccoli Cheddar Egg Bites
Italian Sausage and Arugula Quiche
Old Fashioned Breakfast Casserole
Croque Monsieur Breakfast Casserole
Print Recipe
Ingredients
- 4 tablespoons unsalted butter, melted and cooled, plus more for greasing
- 5 cups torn day-old croissant cubes (about 3 to 4 large croissants)
- 1/2 pound thinly sliced Black Forest ham, roughly chopped
- 1½ cups shredded Gruyère, divided
- 8 large eggs
- 1½ cups whole milk
- 1/2 cup whole milk Greek yogurt
- 1 teaspoon kosher salt
- 1 teaspoon freshly ground black pepper
- 1 teaspoon garlic powder
- 1 tablespoon Dijon mustard
- 1 tablespoon fresh thyme leaves, plus more for garnish
- 1/2 cup grated Parmesan cheese
Instructions
- Position one oven rack in the middle and one near the top. Preheat the oven to 375°F. Grease a 9×13-inch baking dish with butter.
- Arrange torn croissant pieces in a single layer in the prepared dish. Scatter ham and 1 cup Gruyère over the croissants.
- Whisk together melted butter, eggs, milk, yogurt, salt, pepper, garlic powder, Dijon, and thyme until combined.
- Pour the egg mixture over the croissants, making sure pieces are evenly coated. Top with remaining 1/2 cup Gruyère and the Parmesan.
- Bake on the middle rack for 30 minutes. Move to the higher rack and bake 15–20 more minutes, until the top is deeply golden and the center is set.
- Cool 10–15 minutes, garnish with thyme, cut into 8 squares, and serve.
Nutrition
Carbohydrates: 72 g,
Protein: 36 g,
Fat: 57 g
Nutrition information is an approximation and should be used as a guide.
Additional Info
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Photography and styling by Eat Love Eats.