Overnight Croque Monsieur Casserole Recipe

Introduction

This Overnight Croque Monsieur Casserole is a decadent twist on the classic French sandwich, perfect for a make-ahead breakfast or brunch. Layers of buttery bread, savory Canadian bacon, and melty Gruyere soaked in a flavorful custard create a rich and comforting dish that serves a crowd.

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 onion, season with salt, stir, and cook until just softened, about 3 to 4 minutes. Then add garlic, season with salt and pepper, and cook until beginning to soften and fragrant, about 1 minute. Remove from heat and stir in thyme.
3. Step 3: Whisk together eggs, half-and-half, mustard, hot sauce, and salt in a large bowl until evenly combined. Arrange half of the cubed bread in bottom of prepared dish. Sprinkle with 1 cup Gruyere and half each of onion-garlic mixture and ham. Repeat layering with remaining bread, onion mixture, ham, and Gruyere cheese. Pour egg mixture over top.
4. Step 4: Press down on bread to fully submerge in egg custard, cover with plastic wrap, and weigh down with a heavy plate. Refrigerate for 3 to 12 hours.
5. Step 5: When ready to bake, remove weight and plastic wrap from casserole, cover with aluminum foil, and place in oven on middle rack. Set oven temperature to 325°F (no need to preheat) and bake for 35 minutes. Remove foil and increase temperature to 375°F. Sprinkle parmesan over the strata and bake for another 10 to 15 minutes until golden brown.
6. Step 6: Remove from oven and sprinkle over remaining thyme. Allow to cool for at least 5 minutes. Serve with hot sauce on the side.

Tips & Variations

• Use day-old or slightly toasted bread to help absorb the custard without becoming too soggy.
• Swap Canadian bacon for ham or cooked pancetta for a different flavor profile.
• For a vegetarian version, omit the meat and add sautéed mushrooms or spinach instead.
• Make sure to press the bread well into the custard to ensure even soaking and a cohesive bake.

Storage

Store leftovers in an airtight container 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 can also be frozen before baking; thaw overnight in the refrigerator and bake as directed.

How to Serve

Serve this delicious recipe with your favorite sides.

FAQs

Can I prepare this casserole the morning I want to serve it?

Yes, you can refrigerate it for as little as 3 hours before baking, but allowing it to soak overnight helps the flavors meld and the bread fully absorb the custard for the best texture.

What if I don’t have Gruyere cheese?

Swiss cheese is a good substitute and will provide a similar meltiness and mild flavor. For a stronger taste, try Emmental or Jarlsberg cheese.

Overnight Croque Monsieur Casserole Recipe

Print Recipe

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4.4 from 64 reviews

This Overnight Croque Monsieur Casserole is a delightful twist on the classic French sandwich, layered with butter bread, Canadian bacon, Gruyere cheese, and a flavorful custard infused with garlic, onions, and thyme. Prepared the night before and baked to golden perfection, this savory casserole offers a rich and comforting breakfast or brunch option that serves a crowd.

• Author: Maya
• Prep Time: 20 minutes
• Cook Time: 50 minutes
• Total Time: 3 hours 10 minutes to 12 hours 50 minutes (including soaking time)
• Yield: 12 servings 1x
• Category: Breakfast Casserole
• Method: Baking
• Cuisine: French-inspired

Ingredients

Scale 1x2x3x

For the Custard and Flavor Base

• 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 one 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

Main Ingredients

• 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 the Baking Dish: Coat a 3-quart (13×9-inch) baking dish generously with butter and set aside to prevent sticking during baking.
2. Sauté Aromatics: Heat a large frying pan over medium heat and melt the tablespoon of butter until slightly frothy. Add the chopped onion, season with salt, and cook for about 3 to 4 minutes until softened. Then add the garlic slices, season with salt and pepper, and cook for another 1 minute until fragrant. Remove from heat and stir in the chopped fresh thyme for added flavor.
3. Mix Custard: In a large bowl, whisk together the eggs, half-and-half, Dijon mustard, hot sauce, and kosher salt until the mixture is smooth and well combined.
4. Assemble the Casserole: Arrange half of the thick bread cubes evenly at the bottom of the prepared baking dish. Sprinkle half of the shredded Gruyere, followed by half of the sautéed onion-garlic mixture, and half of the diced Canadian bacon. Repeat the layering process with the remaining bread, onion mixture, ham, and Gruyere cheese. Pour the egg custard evenly over the assembled layers.
5. Soak Overnight: Press down firmly on the bread to ensure it is fully submerged 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 let the flavors meld and the bread soak thoroughly.
6. Bake Covered: When ready to bake, remove the plastic wrap and weight from the casserole. Cover the dish with aluminum foil and place it in the oven on the middle rack. Set the oven temperature to 325°F (you do not need to preheat) and bake for 35 minutes to gently cook the custard.
7. Finish Baking and Brown: Remove the foil, sprinkle the finely grated Parmesan cheese over the top of the casserole, and increase the oven temperature to 375°F. Bake uncovered for another 10 to 15 minutes until the top is golden brown and bubbly.
8. Garnish and Serve: Take the casserole out of the oven and sprinkle the remaining fresh thyme on top. Let it cool for at least 5 minutes before serving. Offer hot sauce on the side for an optional spicy kick.

Notes

• For best results, use stale or toasted butter bread to prevent the casserole from becoming too soggy.
• The casserole can be refrigerated overnight and baked the next morning for a convenient make-ahead breakfast or brunch.
• You can substitute Canadian bacon with smoked ham or regular cooked ham according to preference.
• Adjust the amount of hot sauce to taste for milder or spicier casseroles.
• Leftovers can be stored in an airtight container in the refrigerator for up to 3 days and reheated gently in the oven.

Keywords: Overnight Croque Monsieur, Breakfast Casserole, French Breakfast, Gruyere Casserole, Make Ahead Breakfast