Skip to Content

Croissant Breakfast Casserole

Looking for a delicious overnight breakfast casserole recipe for your holiday celebrations? This savory Croissant Breakfast Casserole is full of ham, mushrooms, and gruyere cheese for a breakfast that will satisfy all of your guests.

Slice of croissant breakfast casserole and two pieces of grapefruit on a white plate

This post is sponsored by Challenge Butter. Thank you for continuing to support the brands that make My Baking Addiction possible.

Holiday mornings are something else, aren’t they?

I find that whether we have family staying with us or it’s just Eric, Elle and me, everyone wakes up starving and anxious to watch the parade (if it’s Thanksgiving) or open presents or just hang out. And somehow they all come to me wondering what’s for breakfast.

That’s when I turn to recipes I can prep the night before and bake off in the morning. I want something so easy to cook that I don’t even have to have had my coffee yet to be able to pop it in the oven.

This year, I’m all about this savory, buttery Croissant Breakfast Casserole.

Ingredients for croissant breakfast casserole arranged on a marble countertop

SAVORY CROISSANT BREAKFAST CASSEROLE

Recipes like Make-Ahead Breakfast Casserole, Overnight French Toast Casserole, and Easy Pecan Sticky Buns have all been big hits in the past for my family. They think they’re delicious and I love them because they’re so easy to make.

It’s great when we can all win, right?

This Croissant Breakfast Casserole is another winner. I was inspired to try using croissants from the bakery section of my grocery store and turn them into a savory breakfast casserole. 

Mushroom and leek filling for croissant breakfast casserole in a skillet

Something about the croissants must have gotten me into a French mindset, because I found myself gathering up ham, mushrooms, leeks, gruyere cheese, and – of course – Challenge Unsalted Butter for this casserole.

If you’ve ever had a croque monsieur, this tastes a little like the breakfast casserole version of that. 

Does this sound fancy? Sure. Will your guests think you’re fancy when you serve it to them? Probably. Is it hard to make? Not at all. Promise.

Beaten eggs, milk, cheese, and mushroom filling in a large glass mixing bowl

HOW TO MAKE THIS OVERNIGHT BREAKFAST CASSEROLE

This breakfast casserole is made in 4 basic steps:

  • Saute the filling
  • Mix the casserole together
  • Cover and chill overnight
  • Bake in the morning

To start the filling, melt 4 tablespoons of Challenge Unsalted Butter in a pan over medium heat. 

Croissant breakfast casserole mixture in a glass mixing bowl

I like starting with Challenge Butter for this recipe because it is churned daily from the freshest milk and made without any artificial preservatives, fillers, or dyes. Its flavor and quality make it absolutely perfect for sauteing the mushrooms and leeks that will go into our casserole.

When the butter is melted, add the mushrooms, leeks, and onion with a pinch of salt. Let those cook for about 10 minutes; we want all of those vegetables to be soft and caramelized before adding garlic, whole grain mustard, and a splash of sherry vinegar to the pan.

Unbaked croissant breakfast casserole in a white baking dish set on a marble countertop

Let the filling cool while you whisk together 8 eggs and 2 cups of whole milk. Add in the cooled filling, diced ham, gruyere and parmesan cheese, and some more salt and pepper. 

Now you’ll gently fold in croissants that you have torn or cut into 1-inch pieces. Since the croissants are pretty delicate, make sure you use a gentle hand here so they don’t totally fall apart.

Overhead view of baked croissant breakfast casserole in a white baking dish on a marble countertop

Generously butter a 9×13-inch baking dish with more Challenge Butter. Add the casserole mixture to the pan, then cover and refrigerate overnight.

In the morning, preheat the oven to 375ºF and bake the casserole for 1 hour. It’s ready when the top is golden, the edges are crispy, and the center is set.

Baked croissant breakfast casserole in a white baking dish set on a white countertop

RECIPE VARIATIONS

I adore mushrooms, so this Croissant Breakfast Casserole is right up my alley. If you aren’t a big fan of mushrooms, though, you can definitely change up the vegetables!

If you don’t want to go with mushrooms, try making the casserole with broccoli instead. It goes great with the ham and cheese in the recipe. You could even try asparagus if you want!

Two white plates holding slices of croissant breakfast casserole and slices of grapefruit alongside a baking dish of breakfast casserole

If you’re having a hard time finding gruyere, a sharp white cheddar would be delicious in this recipe as well. 

No matter what cheese or vegetables you choose, this Croissant Breakfast Casserole will be a great addition to your holiday menus.

Overhead view of a slice of croissant breakfast casserole on a plate alongside two pieces of grapefruit
Slice of croissant breakfast casserole and two pieces of grapefruit on a white plate

Croissant Breakfast Casserole

Yield: 8-10 servings
Prep Time: 20 minutes
Cook Time: 1 hour
Chill Time: 8 hours
Total Time: 9 hours 20 minutes

Looking for a delicious overnight breakfast casserole recipe for your holiday celebrations? This savory Croissant Breakfast Casserole is full of ham, mushrooms, and gruyere cheese for a breakfast that will satisfy all of your guests.

Ingredients

  • ¼ cup Challenge Unsalted Butter, plus extra for buttering the pan
  • 8 ounces sliced fresh mushrooms, such as crimini or shiitake
  • 1 large leek, sliced
  • 1 medium onion, diced
  • 1 teaspoon fine sea salt, divided
  • 3-4 cloves minced garlic
  • 2 tablespoons whole-grain mustard
  • 1 tablespoon sherry vinegar (optional)
  • 8 large eggs
  • 2 cups whole milk
  • 6-8 ounces diced smoked ham
  • 6 ounces grated Gruyere cheese
  • 2 ounces freshly grated parmesan cheese
  • ½ teaspoon black pepper
  • 12 ounces croissants, cut or torn into 1-inch pieces

Instructions

  1. In medium pan, melt the butter over medium heat. Add the mushrooms, leeks, and onion with ¼ teaspoon of the salt. Saute for about 10 minutes. When the mushrooms and onions are soft and caramelized, add the garlic, mustard, and sherry vinegar and cook for 1 additional minute. Set aside to cool.
  2. In a large bowl, whisk the eggs and milk until thoroughly combined. Add the cooled mushroom mixture, ham, cheeses, and black pepper, and remaining ¾ teaspoon of salt. Gently fold in the croissant pieces. 
  3. Generously butter a 9x13-inch baking dish. Add the casserole mixture to the pan. Cover and refrigerate overnight. 
  4. In the morning, preheat the oven to 375ºF. Bake the casserole for 1 hour, or until the top is golden, the edges are crispy, and the center is set.
Nutrition Information
Yield 10
Amount Per Serving Calories 556Total Fat 29gSaturated Fat 15gTrans Fat 0gUnsaturated Fat 11gCholesterol 245mgSodium 1952mgCarbohydrates 33gFiber 2gSugar 8gProtein 42g

Did you make this recipe?

Tag me on social! I want to see what you made! @jamiemba

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Pat Monaghan

Friday 19th of November 2021

Hi, I am a little confused how many croissants. Receipe shows 12 ounces croissants, why the ounces? Is it 12 croissants? Thanks, Pat

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Skip to Recipe