Overnight Croque Monsieur Casserole Recipe

Introduction

This Overnight Croque Monsieur Casserole is a rich and savory breakfast or brunch dish inspired by the classic French sandwich. With layers of buttery bread, caramelized onions, garlic, Canadian bacon, and melted Gruyere cheese, it’s a comforting meal that you can prepare ahead and bake in the morning.

Ingredients

• 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
• 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
• 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

1. Step 1: Coat a 3-quart (13×9-inch) baking dish with butter and set aside.
2. Step 2: Place a large frying pan over medium heat and add butter. When butter is slightly frothy, add chopped onion, season with salt, and cook until just softened, about 3 to 4 minutes. Add sliced garlic, season with salt and pepper, and cook until fragrant, about 1 minute. Remove from heat and stir in fresh thyme.
3. Step 3: In a large bowl, whisk together eggs, half-and-half, Dijon mustard, hot sauce, and kosher salt until evenly combined. Arrange half of the cubed bread in the bottom of the prepared dish. Sprinkle with 1 cup Gruyere cheese, half of the onion-garlic mixture, and half of the Canadian bacon. Repeat layering with remaining bread, onion mixture, ham, and Gruyere. Pour the egg mixture evenly over the top.
4. Step 4: Press down on the bread cubes to fully submerge them in the egg custard. Cover the dish with plastic wrap and place a heavy plate on top to weigh it down. Refrigerate for 3 to 12 hours to allow flavors to meld and bread to soak.
5. Step 5: When ready to bake, remove the weight and plastic wrap. Cover the casserole with aluminum foil and place it on the middle rack of the oven. Set the oven temperature to 325°F (no need to preheat) and bake for 35 minutes. Remove the foil, sprinkle grated Parmesan cheese over the top, and increase the oven temperature to 375°F. Bake for an additional 10 to 15 minutes until golden brown and bubbly.
6. Step 6: Remove from oven and sprinkle with the remaining fresh thyme. Let the casserole cool for at least 5 minutes before serving. Serve with extra hot sauce on the side if desired.

Tips & Variations

• Use stale or toasted bread to prevent sogginess and help the casserole hold its shape.
• Substitute Canadian bacon with cooked ham or smoked turkey for a different flavor.
• For a vegetarian version, omit the Canadian bacon and add sautéed mushrooms or spinach instead.
• If you prefer a sharper cheese flavor, add a bit more Dijon mustard to the custard mixture.

Storage

Store any leftovers covered in the refrigerator for up to 3 days. Reheat individual portions in the microwave or warm in a 350°F oven until heated through. This casserole does not freeze well because of the egg custard, so it’s best enjoyed fresh or refrigerated shortly after baking.

How to Serve

Serve this delicious recipe with your favorite sides.

FAQs

Can I prepare this casserole the morning of serving instead of overnight?

Yes, you can soak the bread and bake immediately, but allowing it to refrigerate overnight helps the bread absorb the custard fully, resulting in a creamier and more flavorful dish.

What can I use if I don’t have Gruyere cheese?

Swiss cheese or Emmental are good substitutes, offering a similar melt and mild nutty flavor. Avoid very strong cheeses that might overpower the other ingredients.

Overnight Croque Monsieur Casserole Recipe

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★★★★★

4.8 from 117 reviews

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.

• Author: Lara
• 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 1x2x3x

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

1. Prepare Baking Dish: Butter a 3-quart (13×9-inch) baking dish generously and set it aside to prevent sticking during baking.
2. 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.
3. 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.
4. 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.
5. 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.
6. 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.
7. 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.
8. 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