There’s nothing better than enjoying this Christmas Morning Casserole with the entire family during the holidays.
This make-ahead croque monsieur inspired casserole is easy to make and packed with delicious ingredients.
Buttery croissants, ham and lots of cheese are enveloped by a custardy egg mixture which is baked until golden brown. It’s a delicious casserole that’s a must-make during the holiday season!
I love my Mom’s recipe for quiche for a savory Christmas morning breakfast or my spiced pear french toast casserole for a sweet option. But, this Christmas Morning Casserole is the perfect recipe to feed a crown with a similar savory flavor to quiche. It’s great for holiday brunch with the whole family!
Why you’ll love this Christmas breakfast casserole recipe
- Make-Ahead: You can prep this casserole on Christmas Eve, refrigerate it and bake it the next morning!
- Easy: Easy to find ingredients are all that is needed.
- Versatile: There are easy substitutions for ingredients depending on your tastes.
Ingredients
Croissants: make sure to buy large croissants for this overnight breakfast casserole
Ham: I like to use sliced black forest ham but you could also use honey ham
Cheese: I love to use salty, nutty gruyere cheese in this Christmas casserole recipe
Leeks: leeks add a gorgeous flavour to complement the ham and gruyere cheese
Butter: butter is a must for sautéing the leeks
Eggs: you will need 8 eggs to make this recipe
Milk: whole milk adds a nice richness to the egg mixture but you could swap for 2% milk if desired
Seasonings: a combination of dijon mustard, dried thyme, garlic powder, kosher salt, ground black pepper, and ground nutmeg round out the flavour profile
How to make this easy breakfast casserole recipe
- Preheat the oven to 350F and grease a 9×13 inch baking dish with nonstick cooking spray or with butter.
- In a medium frying pan set over medium heat add 2 tablespoons of butter. Once the butter is melted and starting to bubble, add the chopped leeks and cook, stirring often until just softened, 4-5 minutes. Set aside.
- When the oven is preheated, add the torn croissants to the greased baking dish, spread out into a fairly even layer (it’s ok if some pieces overlap) and bake in the oven for 5 minutes. Remove from the oven and set aside.
- In a large bowl make the egg mixture by whisking together the cooked leeks, eggs, whole milk, dijon mustard, dried thyme, garlic powder, kosher salt, ground pepper and ground nutmeg until well combined. Once well combined, whisk in 1 cup of the shredded gruyere cheese until well combined. Set aside.
- Distribute 3/4 cup of the torn ham in between the croissants in the baking dish.
- Slowly pour the egg mixture evenly over the croissants and ham in the baking dish. Finish by sprinkling the remaining 1 ½ cups shredded gruyere cheese over top of the casserole and then nestle the remaining ¼ cup of torn ham into the cheese.
- Cover with foil and let stand at room temperature for 30-45 minutes before baking. Or, cover tightly with foil or plastic wrap and refrigerate overnight (about 12 hours).
- If the dish has been refrigerated, remove from the refrigerator, remove the foil and let it stand at room temperature for 30 minutes before preheating the oven to 350F and baking.
- Remove the layer of aluminum foil before baking!
- Bake until the egg mixture is set and the top is bubbling, golden brown and puffed up, about 40-45 minutes. (You may need 10-15 minutes more baking time if baking straight from the refrigerator).
- Let cool for 5-10 minutes before serving garnished with fresh thyme leaves.
What to serve with Christmas Morning Casserole
- Arugula Salad: Dress arugula with lemon juice and olive oil for a refreshing complement to the ham and cheese in the casserole.
- Fresh fruits: Add a fresh fruit platter or cut seasonal fruits of choice which are a nice, fresh taste beside the hearty breakfast casserole.
- Kale Salad: This Kale & Brussels Salad is a simple recipe that can be prepped ahead of time too.
Tips & Tricks
- Make sure to shred all of the cheese yourself. I do not recommend using packaged shredded cheese as it does not melt as well.
- A good substitute for leeks are 1 cup chopped green onions; 2 shallots, diced; or, 1/2 yellow onion diced.
- Don’t skip the mustard! Even if you’re not a fan of mustard, it helps to cut the rich flavours of the eggs and cheese.
- Make this up to 12 hours ahead of time. Note that if baking after refrigerated, you may need 10-15 minutes more baking time if baking straight from the refrigerator.
Common Questions
A good substitute for gruyere cheese is Emmental, Swiss cheese or Comté cheese. In a pinch you could also use a sharp cheddar cheese.
How to store leftover casserole
Allow the baked casserole to cool completely before cutting into individual portions. Then, store the portions in an airtight container in the fridge for up to 3-4 days. Reheat leftovers in the oven, covered, at 325F until warmed through or you could warm using the microwave.
More great recipes to make for Christmas morning
- Easy French Toast Blueberry Breakfast Bake Recipe
- Savoury Turkey Breakfast Sausage Egg Muffins
- Cranberry Chocolate Scones with Orange Glaze
Make-Ahead Christmas Morning Breakfast Casserole
Ingredients
- 6 large croissants, roughly torn
- 1 cup (about 5oz / 140grams) packed sliced black forest or honey ham
- 1 cup chopped leeks, white and light green parts (about 1 large leek)
- 2 tbsp butter
- 8 eggs
- 2 cups whole milk
- 2 tsp dijon mustard
- 1 tsp dried thyme
- ½ tsp garlic powder
- 1 ¼ tsp kosher salt
- ½ tsp ground pepper
- ¼ tsp ground nutmeg
- 2 ½ cups shredded gruyere cheese
- Fresh thyme leaves and fresh ground pepper to garnish
Instructions
- Preheat the oven to 350F and grease a 9×13 inch baking dish with nonstick cooking spray or with butter.
- In a medium frying pan set over medium heat add 2 tablespoons of butter. Once the butter is melted and starting to bubble, add the chopped leeks and cook, stirring often until just softened, 4-5 minutes. Set aside.
- When the oven is preheated, add the torn croissants to the greased baking dish, spread out into a fairly even layer (it’s ok if some pieces overlap) and bake in the oven for 5 minutes. Remove from the oven and set aside.
- In a large bowl make the egg mixture by whisking together the cooked leeks, eggs, whole milk, dijon mustard, dried thyme, garlic powder, kosher salt, ground pepper and ground nutmeg until well combined. Once well combined, whisk in 1 cup of the shredded gruyere cheese until well combined. Set aside.
- Distribute 3/4 cup of the torn ham in between the croissants in the baking dish.
- Slowly pour the egg mixture evenly over the croissants and ham in the baking dish. Finish by sprinkling the remaining 1 ½ cups shredded gruyere cheese over top of the casserole and then nestle the remaining ¼ cup of torn ham into the cheese.
- Cover with foil and let stand at room temperature for 30-45 minutes before baking. Or, cover tightly with foil or plastic wrap and refrigerate for up to 12 hours.
- If the dish has been refrigerated, remove from the refrigerator, remove the foil and let it stand at room temperature for 30 minutes before preheating the oven to 350F.
- Remove the layer of aluminum foil before baking!
- Bake until the egg mixture is set and the top is bubbling, golden brown and puffed up, about 40-45 minutes. (You may need 10-15 minutes more baking time if baking straight from the refrigerator).
- Let cool for 5-10 minutes before serving garnished with fresh thyme leaves.
Notes
- Make sure to shred all of the cheese yourself. I do not recommend using packaged shredded cheese as it does not melt as well.
- A good substitute for gruyere cheese is Emmental, Swiss cheese or Comté cheese. In a pinch you could also use a sharp cheddar cheese.
- A good substitute for leeks are 1 cup chopped green onions; 2 shallots, diced; or, 1/2 yellow onion diced.
Photography by: Kaeleigh Pugliese
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