Croque Monsieur breakfast casserole is made with baguette slices layered with ham and Dijon mustard, then topped with creamy béchamel sauce and Gruyére cheese for a melty, gooey, top with crispy edges. You can assemble it one day ahead and bake the next morning for holidays and brunch gatherings!
Give us a cheesy breakfast casserole, but make it French! I mean, the French do cheesy and gooey pretty well, so let’s make it in the image of the classic Croque Monsieur sandwich that I enjoyed eating so much during my travels through France.
My coworkers at the office are my taste-testers and they were raving about this recipe. The texture of the baguette, the velvety sauce, the creaminess of the melted cheese, and that bite of Dijon = breakfast casserole heaven!
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Croque Monsieur breakfast casserole ingredients
- Baguettes: Texture! Texture! Texture! All that crust gets crispy on top and adds satisfying chewy texture in the middle.
- Gruyére cheese: Gruyère is a swiss cheese that melts really well, and is used in lots of cheesy French brunch recipes like my Asparagus Gruyere Quiche!
- Thinly sliced ham: But GOOD ham. Like, it should still actually look like ham. Avoid the overly-processed lunch meat variety.
- Eggs and half & half: This will be our custard to hold everything together and give us that French toast kind of vibe in the middle.
- Béchamel sauce: Flour, butter, whole milk. We'll add some of the cheese to it to make an actual French cheese sauce called mornay sauce.
- Dijon mustard: This peppery, tangy bite of acid is just what's needed to break through all the dairy and cheesiness.
*Ingredients with measurements are listed in the recipe card below.
How to make croque monsieur breakfast casserole
Step 1: Get the bread stale and grate the cheese
Preheat the oven to 300°F. Cut the baguettes into ยฝ inch slices and divide between two sheet pans. Cook the bread in the oven for 10-15 minutes, flipping the slices over occasionally, until they feel stale and very lightly toasted.
Use a box grater or a food processor to grate the Gruyère and set aside.
Debra's tip: Grate your own cheese!
One of my top cooking tips is to grate your own cheese. Yes, pre-grated will work, but it has anti-caking agents on it that can affect the way it melts and add a grainy texture. Grate the cheese yourself either on a box grater or in the food processor and you'll have creamier tasting and better-melting cheese!
Step 2: Start layering the casserole
Increase the oven temperature to 350°F. Lay about half of the baguette slices in the bottom of the casserole dish, fit them together as tightly as possible, but keep them level.
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Spread the Dijon mustard on the remaining baguette slices, then shingle them in three rows on top of the slices in the bottom of the casserole.
Break the ham apart and place one small piece in between each slice of bread.
Step 3: Make the custard
Add eggs to a large mixing bowl and beat lightly, add the half and half and ยฝ teaspoon of kosher salt and whisk to combine.
Pour the custard over the layered bread slices and place in the refrigerator for 30 minutes while you make the béchamel sauce. If you'd like to make it ahead, at this point, you can cover the casserole and refrigerate overnight.
Step 4: Make the béchamel (mornay sauce)
Melt the butter in a sauce pan over medium heat.
Add flour and whisk constantly for about one minute.
Add the milk and bring to a boil keeping the heat medium, whisking almost constantly until the sauce has reduced by about โ and is thick enough to coat the back of a spoon. Remove from heat and stir in โ cup of the grated gruyere and ยผ teaspoon of kosher salt.
Step 5: Top with sauce, cheese and bake!
Remove the casserole from the refrigerator and pour the sauce over the top, try to leave some spots with the crust of baguette peeking through to give you some crispy edges!
Top with remaining โ cup gruyere cheese.
Bake for 35-40 minutes until the cheese is bubbly and just beginning to brown. Switch the oven to broil and cook until the top is golden brown and the edges of the bread are crispy! Let stand about 5-10 minutes before serving.
Baguettes are the best bread for this casserole
I tested this with different kinds of bread, and I thought to myself, is it really worth it to take the time to slather mustard on all these tiny pieces of bread? Oh yes, I promise you, it is. Really and truly.
Not only are you keeping it super French by using a baguette, you get that crispy crust on top and texture throughout because you've got crust all the way around! The crust keeps the center of the bread from seeming mushy, instead giving a luscious custardy texture. Yum!
More brunch recipes
Debra's Details: Croque Monsieur breakfast casserole is easy, cheesy, and satisfying!
- All the flavor you love from the classic sandwich in casserole form!
- Using baguettes make all the difference - the texture takes this casserole over the top!
- Assemble it the night before and bake the next day for easy holiday meal planning.
- Cheese in the béchamel sauce + cheese on top makes it cheesy to the max!
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Recipe
Cheesy Croque Monsieur Breakfast Casserole
Ingredients
Casserole
- 2 baguettes
- 1 cup grated gruyere cheese (divided)
- 3 tablespoons dijon mustard (approximately)
- 6 ounces thinly sliced ham
- 4 eggs
- 2 cups half and half
- ½ teaspoon kosher salt
Bechamel sauce
- 2 tablespoons unsalted butter
- 2 tablespoons flour
- 1 cup whole milk
- ¼ teaspoon kosher salt
Instructions
- Preheat the oven to 300°F. Cut the baguettes into ½ inch slices and divide between two sheet pans. Cook the bread in the oven for 10-15 minutes, flipping the slices over occasionally, until they feel stale and very lightly toasted.
- Use a box grater or a food processor to grate the Gruyère and set aside.
- Increase the oven temperature to 350°F.
- Lay about half of the baguette slices in the bottom of the casserole dish, fit them together as tightly as possible, but keep them level.
- Spread the Dijon mustard on the remaining baguette slices, then shingle them in three rows on top of the slices in the bottom of the casserole.
- Break the ham apart and place one small piece in between each slice of bread.
- Add the eggs to a large mixing bowl and beat lightly, add half and half and ½ teaspoon of kosher salt, whisk to combine. Pour the custard over the layered bread slices and place in the refrigerator for 30 minutes while you make the béchamel sauce. (If you'd like to make it ahead, at this point, you can cover the casserole and refrigerate overnight.)
- Melt the butter in a sauce pan over medium heat. Add flour and whisk constantly for about one minute.
- Add the milk and bring to a boil (keep the heat medium), whisking almost constantly until the sauce has reduced by about ⅓ and is thick enough to coat the back of a spoon. Remove from heat and stir in ⅓ cup of the grated gruyere and ¼ teaspoon of kosher salt. Taste and adjust seasoning if necessary.
- Remove the casserole from the refrigerator and pour the sauce over the top, try to leave some spots with the crust of baguette peeking through to give you some crispy edges! Top with remaining ⅔ cup gruyere cheese.
- Bake for 35-40 minutes until the cheese is bubbly and just beginning to brown. Switch the oven to broil and cook until the top is golden brown and the edges of the bread are crispy! (Do NOT walk away from something under the broiler, see note.) Let stand about 5-10 minutes before serving.
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I will email this recipe to you, so you can come back to it later!
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Notes
- Baguettes are best: I tested this with different kinds of bread, and I thought to myself, is it really worth it to take the time to slather mustard on all these tiny pieces of bread? Oh yes, I promise you, it is. Really and truly. Not only are you keeping it super French by using a baguette, you get that crispy crust on top and texture throughout because you've got crust all the way around! The crust keeps the center of the bread from seeming mushy, instead giving a luscious custardy texture. Yum!
- Never leave something under the broiler unattended! Broiling can turn to burning QUICKLY! Stay close by and check frequently when broiling the top of the casserole.
- Béchamel sauce can be made up to 1 week ahead of time. Transfer it to an airtight container, then cover the surface with a bit of plastic wrap before you put the lid on to keep a skin from forming. Reheat in a sauce pan over low heat, then add cheese and pour over the casserole. If the sauce has gotten too thick, add a tablespoon or two of milk until it reaches the proper consistency.
- The casserole can be assembled the night before up to the point of pouring the custard over the bread (step 7 above.) Cover it tightly and refrigerate overnight. Top with sauce and remaining cheese the next morning before baking.
Nutrition
Nutrition information is automatically calculated as an estimate. Calorie accuracy is not guaranteed.
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