Overnight Croque Monsieur Casserole Recipe
This Overnight Croque Monsieur Casserole is a decadent, make-ahead breakfast or brunch dish featuring layers of buttery bread, savory Canadian bacon, melted Gruyere, and a fragrant onion-garlic thyme custard. Prepared the night before and baked to golden perfection in the morning, it delivers rich flavors and a perfectly creamy texture with minimal morning prep.
- Prep Time: 20 minutes
- Cook Time: 50 minutes
- Total Time: 3 hours 20 minutes to 12 hours 50 minutes (including soak time)
- Yield: 12 servings 1x
- Category: Breakfast, Brunch, Casserole
- Method: Baking
- Cuisine: French-American
Ingredients
Scale
Butter and Aromatics
- 1 Tablespoon Unsalted Butter, plus more to coat pan
- 1 Yellow Onion, roughly chopped (about 1 1/2 cups)
- 4 Cloves Garlic, thinly sliced
- Salt and Pepper, to taste
- 1 Tablespoon Fresh Thyme, roughly chopped, plus 1 teaspoon for garnish
Egg Custard
- 8 Large Eggs
- 1 1/2 Cups Half-and-Half
- 2 Tablespoons Dijon Mustard
- 1/2 Teaspoon Hot Sauce, plus more for garnish
- 1 1/2 Teaspoons Kosher Salt
Main components
- 1 Loaf Martin’s Old-Fashioned Real Butter Bread, stale or toasted, cut into thick cubes
- 2 Cups Gruyere Cheese, shredded (about 4.5 ounces)
- 1/2 Pound Canadian Bacon, cut into 1/2-inch dice
- 1/4 Cup Parmesan Cheese, finely grated (about 1 ounce)
Instructions
- Prepare Baking Dish: Butter a 3-quart (13×9-inch) baking dish generously and set it aside to prevent sticking during baking.
- Cook Aromatics: Heat butter in a large frying pan over medium heat until slightly frothy. Add the chopped onion, season with salt, and cook until softened, about 3 to 4 minutes. Add the sliced garlic, season with salt and pepper, and cook until fragrant and beginning to soften, about 1 minute. Remove from heat and stir in the fresh thyme.
- Make Egg Mixture: In a large bowl, whisk together the eggs, half-and-half, Dijon mustard, hot sauce, and kosher salt until the mixture is smooth and fully combined.
- Assemble Casserole: Layer half of the bread cubes evenly in the bottom of the prepared baking dish. Sprinkle half of the shredded Gruyere cheese on top, followed by half of the onion-garlic mixture and half of the diced Canadian bacon. Repeat the layers with the remaining bread, onion mixture, ham, and Gruyere. Carefully pour the egg custard evenly over the entire casserole.
- Soak Overnight: Press down gently on the bread to submerge it completely in the egg custard. Cover the dish tightly with plastic wrap and weigh it down with a heavy plate. Refrigerate for 3 to 12 hours to allow the bread to soak up the custard fully.
- Bake Covered: When ready to bake, remove the plastic wrap and weight. Cover the casserole with aluminum foil and place it on the middle rack of the oven. Without preheating, set the oven to 325°F and bake for 35 minutes.
- Bake Uncovered: Remove the foil, sprinkle the finely grated Parmesan cheese over the top, then increase the oven temperature to 375°F. Continue baking uncovered for an additional 10 to 15 minutes until the top is golden brown and the casserole is fully set.
- Garnish and Serve: Remove the casserole from the oven, sprinkle with the remaining fresh thyme, and allow it to cool for at least 5 minutes before slicing. Serve warm with extra hot sauce on the side if desired.
Notes
- Using stale or toasted bread helps the casserole absorb the custard without becoming too soggy.
- The casserole can be assembled up to 12 hours ahead, making it perfect for stress-free entertaining.
- Be sure to press the casserole down before refrigerating to ensure the bread soaks evenly.
- If you prefer, substitute Canadian bacon with ham or smoked turkey for variation.
- Leftovers can be stored covered in the refrigerator for up to 3 days and reheated gently.
Keywords: Croque Monsieur casserole, overnight casserole, breakfast casserole, brunch recipe, Gruyere cheese recipe, Canadian bacon casserole
