This baked croque monsieur casserole turns the classic French sandwich into a rich, cheesy breakfast casserole with ham, Gruyère, custardy bread, and creamy béchamel. It’s an ideal make-ahead brunch recipe for holidays, weekends, or anytime you want the flavor of croque monsieur without standing at the stove.
Why You’ll Love It!
Besides the fact that we took one of the most time consuming, but delicious brunch favs and turned it into a casserole- here are a few more reasons to love it!
- Classic Flavors (plus a new one! )– While this recipes uses Gruyère, Dijon mustard and a classic béchamel sauce laced with nutmeg, it also brings in French flare and little more flavor with sautéed leeks. They are optional, but delicious!
- Overnight Option– I love having the option of preparing this dish the night before, but sometimes that just doesn’t happen so I’ve included how to make it ahead of time and also how to prepare it morning-of.
- Golden Toasty Top– The edges and browned toasties are what people fight over! Instead of baking the sauce right into the casserole, we tested it baked with custard and then used the sauce at the end to preserve those delicious little crunchy pieces.
Recipe Essentials
You might just have a lot of these baked croque monsieur casserole ingredients already on hand. A full list of ingredients with measurements for this recipe is available in the printable recipe card below.
- Bread – I like to use sourdough, but you could also use brioche or country loaf. It’s best for it to be a little stale (1-2 days old) so that it doesn’t become soggy immediately.
- Ham – Deli ham or leftover ham can also be used. Black forest is the pick for me if I’m grabbing deli ham.
- Salted butter
- Leek
- Eggs
- Half and half
- Dijon mustard
- Coarse kosher salt
- Ground black pepper
- Swiss cheese
- Gruyere cheese
- Flour
- Whole milk
- Nutmeg
- Parmesan cheese
- Chives
How to Make Baked Croque Monsieur Casserole (Step-by-Step)
You can have your new favorite breakfast casserole ready in no time following these simple steps.
- Prepare oven and pan. Preheat the oven and grease or spray a baking dish. Place the cubed bread and ham into the baking dish, toss lightly. Set aside.
- Clean Leeks. Leeks require unique cleaning. Watch my quick video on how to clean leeks.
- Sauté leeks. Melt butter in a small saucepan over medium heat. Add the cut leeks, sautéing until soft. Evenly divide them over the bread and ham.
- Combine eggs, half and half, mustard and seasonings. Melt remaining butter in the microwave. In a medium mixing bowl, combine the melted butter, eggs, half & half, Dijon mustard, Kosher salt and black pepper.
- Pour custard over bread. Pour half of the custard mixture over the bread, tossing and pressing down gently to get the custard to absorb into the bread. Pour the remaining over top and repeat the pressing and tossing. Add the shredded cheese, tossing again so the cheese is evenly distributed.
- Cover with aluminum foil and bake. Remove the foil and continue to bake until the internal temperature reaches 160°F using a digital thermometer. Remove and top with the grated parmesan cheese, returning to the oven under broil until the top is golden brown and edges are crunchy. Allow the casserole to rest.
- Make sauce. Meanwhile (while the casserole is baking), melt the remaining butter, whisking with the flour until it forms a roux. Allow it to build brown slightly before whisking in the milk. When the sauce has thickened and is smooth, remove from the heat and whisk in the nutmeg, remaining kosher salt and black pepper.
- To serve, the sauce can be spooned over the whole casserole or served on the side in a gravy boat. Sprinkle with chopped chives.
Overnight Instructions (Make-Ahead)
Whether I have the time to make this the night before is a game-time decision, but I do like having the option and it comes with serval scenarios.
- Make the Casserole The Night Before to Soak– Many readers find this one to be the winner and actually love that the custard has more time to soak into the bread. Prepare the casserole through step #4, then cover and chill over night. Give it a quick stir the next morning and let is sit out while the oven preheats to take the chill off.
- Make the Béchamel The Night Before– The creamy sauce can also be made the night before, but will need to be reheated and likely re-seasoned. Do not reheat it in the microwave, instead put it in a saucepan over low heat and add 1-2 tablespoons additional milk to thin it out. Taste it and see it it needs more salt, likely it will only need a pinch.
- Cook The Casserole The Night Before– You can also prepare and bake the casserole the night before and then reheat it the next day. Prepare it through topping it with parmesan cheese, bake at 350°F for 20-25 minutes, checking the internal temperature gets to 165°F and then proceed with the broiler and parmesan cheese.
Make it a Meal
In a French bistro, a croque Monsieur sandwich would likely be accompanied by a simple arugula or spinach salad with a light citrus vinaigrette, fresh fruit or a steamed green veggie like asparagus or green beans.
However, you can serve it with whatever you’d like! Sticking with breakfast favorites, you could pair it with a fresh berry smoothie, some crispy bacon or breakfast sausage or even some crispy home fries.
More Delightful Brunch Bakes
They say that breakfast is the most important meal of the day- and I’s have to agree! Here are some of my breakfast favorites.
Baked Croque Monsieur Casserole Recipe
This Croque Monsieur Casserole layers ham, Gruyère, Dijon, and a silky béchamel for a make-ahead brunch bake with a golden, broiled top.
Servings:
Ingredients
- 5-6 cups sourdough, , brioche or country loaf , 1-2 days old and cut into 2-inch cubes
- 1 ½ cups cubed ham*
- 10 tablespoons salted butter , divided
- 1 leek , whites only, cut into half moons
- 6 eggs
- 1 ¼ cups half-and-half
- 2 tablespoons Dijon mustard
- 1 ½ teaspoons coarse kosher salt , divided
- 1 teaspoon ground black pepper , divided
- 3 cups Swiss or Gruyere cheese , grated and divided
- 2 tablespoons Parmesan cheese , finely grated
- 4 tablespoons flour
- 2 cups whole milk
- 1/4 teaspoon grated nutmeg
- 1 tablespoon chives , chopped
Instructions
- Preheat the oven to 375°F and grease or spray a 9×13 baking dish. Place the cubed 5-6 cups sourdough, , brioche or country loaf and 1 ½ cups cubed ham* into the baking dish, toss lightly. Set aside.
- Melt 1 tablespoon of the butter in a small saucepan over medium heat. Add the cut 1 leek, sautéing until soft. Evenly divide them over the bread and ham.
- Melt 5 tablespoons of the butter in the microwave. In a medium mixing bowl, combine the 5 tablespoons of the melted butter, 6 eggs, 1 ¼ cups half-and-half, 2 tablespoons Dijon mustard, 1 teaspoon of the Kosher salt and ½ teaspoon of the black pepper.
- Pour half of the custard mixture over the bread, tossing and pressing down gently to get the custard to absorb into the bread. Pour the remaining over top and repeat the pressing and tossing. Add the shredded 3 cups Swiss or Gruyere cheese, tossing again so the cheese is evenly distributed.
- Cover with aluminum foil and bake for 25 minutes. Remove the foil and continue to bake for another 15 minutes or until the internal temperature reaches 160°F using a digital thermometer. Remove and top with the grated 2 tablespoons Parmesan cheese, returning to the oven under broil for 1-2 minutes until the top is golden brown and edges are crunchy. Allow the casserole to rest for 5 minutes, bringing it up to 165°F.
- Meanwhile (while the casserole is baking), melt the remaining 4 tablespoons of butter, whisking with the 4 tablespoons flour until it forms a roux. Allow it to build brown slightly before whisking in the 2 cups whole milk. When the sauce has thickened and is smooth, remove from the heat and whisk in the 1/4 teaspoon grated nutmeg, remaining 1 ½ teaspoons coarse kosher salt and 1 teaspoon ground black pepper.
- To serve, the sauce can be spooned over the whole casserole or served on the side in a gravy boat. Sprinkle with chopped 1 tablespoon chives.
- If you've tried this casserole, come back and let us know how it was in the comments or star ratings.
Notes
*Deli ham or leftover ham can also be used. Black forest is the pick for me if I’m grabbing deli ham.
Make Ahead Options:
- Make the Casserole The Night Before to Soak– Many readers find this one to be the winner and actually love that the custard has more time to soak into the bread. Prepare the casserole through step #4, then cover and chill over night. Give it a quick stir the next morning and let is sit out while the oven preheats to take the chill off.
- Make the Béchamel The Night Before– The creamy sauce can also be made the night before, but will need to be reheated and likely re-seasoned. Do not reheat it in the microwave, instead put it in a saucepan over low heat and add 1-2 tablespoons additional milk to thin it out. Taste it and see it it needs more salt, likely it will only need a pinch.
- Cook The Casserole The Night Before– You can also prepare and bake the casserole the night before and then reheat it the next day. Prepare it through topping it with parmesan cheese, bake at 350°F for 20-25 minutes, checking the internal temperature gets to 165°F and then proceed with the broiler and parmesan cheese.
Nutrition
Calories: 375 kcal, Carbohydrates: 13 g, Protein: 19 g, Fat: 28 g, Saturated Fat: 16 g, Polyunsaturated Fat: 2 g, Monounsaturated Fat: 8 g, Trans Fat: 0.4 g, Cholesterol: 165 mg, Sodium: 962 mg, Potassium: 192 mg, Fiber: 1 g, Sugar: 4 g, Vitamin A: 1022 IU, Vitamin C: 1 mg, Calcium: 449 mg, Iron: 1 mg
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