This Croissant Breakfast Casserole is made with buttery croissants, breakfast sausage, leeks and Gruyère baked in a rich egg custard. Assemble it the night before, then bake it in the morning for an easy, cheesy breakfast or brunch that feeds a crowd.
The croissants soak up the egg mixture overnight, staying soft and custardy inside while getting golden and crisp on top.
For another easy make-ahead breakfast, try my hash brown breakfast casserole.
Recipe Summary: Croissant Breakfast Casserole with Sausage and Leeks
- ✅ Recipe Name: Croissant Breakfast Casserole with Sausage and Leeks
- 🕒 Ready In: 1 hour 20 minutes, plus overnight chilling
- 👪 Serves: 12
- 🍽 Calories: 411 per serving
- 🥣 Main Ingredients: Croissants, breakfast sausage, eggs, heavy cream, leeks, Gruyère
- 📖 Dietary Info: Make-ahead friendly, high-protein
- ⭐ Why You'll Love It: Buttery croissants, savory sausage and melty Gruyère make this overnight breakfast casserole rich, cheesy and perfect for an easy brunch or holiday breakfast.
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This Croissant Breakfast Casserole is one of my favorite make-ahead breakfast recipes when I want something rich, cheesy and easy enough for a holiday morning or weekend brunch. Buttery croissants, breakfast sausage, tender leeks and Gruyère are layered with a creamy egg custard, then chilled overnight and baked until golden and set.
Letting the casserole rest overnight gives the croissants time to soak up the egg mixture, so the inside stays soft and custardy while the top gets crisp and browned. If you love savory brunch recipes, try my Puff Pastry Quiche or Cornbread Breakfast Casserole next.
Why you'll love this recipe
- Made the night before. Assemble the entire casserole, cover it and stick it in the refrigerator. Morning-you has very little to do.
- Croissants make it extra good. Instead of regular bread, buttery croissants soak up the savory egg custard and give the casserole a rich, almost strata-like texture.
- It feeds a crowd. One 9x13 casserole makes 12 hearty servings, making it great for holidays and brunch.
- Sausage + Gruyère. Savory breakfast sausage and nutty Gruyère give this plenty of flavor without needing a long list of ingredients.
- The leeks make it different. They cook down until soft and mild and add a subtle onion flavor that works perfectly with the sausage and cheese.
Jump to:
- Recipe Summary: Croissant Breakfast Casserole with Sausage and Leeks
- Why you'll love this recipe
- Key Ingredients
- Variations
- How to make Croissant Breakfast Casserole
- Expert Tips
- Croissant Breakfast Casserole FAQs
- What to Serve with Croissant Breakfast Casserole
- Storing and Reheating
- More Easy Breakfast Casseroles
- Croissant Breakfast Casserole Recipe
Key Ingredients
- Croissants. Soak up the egg custard while staying buttery and crisp on top.
- Breakfast sausage. Use bulk sausage or links with the casings removed. Mild or hot both work.
- Leek. Adds a mild, slightly sweet onion flavor. Clean it well before slicing.
- Eggs and heavy cream. Create the rich, custardy base of the casserole.
- Gruyère. Melty, nutty and perfect with the sausage and leeks. Freshly shredded melts best.
- Seasonings. Garlic powder, salt and black pepper keep the flavors simple and savory.
See the recipe card at the end for the full list of ingredients with the quantities.
Variations
| Change the cheese | Swiss, sharp white cheddar or smoked Gruyère can be used in place of regular Gruyère. |
| Make it spicy | Use hot breakfast sausage or add a pinch of crushed red pepper to the egg mixture. |
| Add vegetables | Sautéed mushrooms or bell peppers would work well with the sausage and leeks. Cook vegetables first so they don't add excess moisture to the casserole. |
| Swap the sausage | Try cooked bacon, diced ham or turkey sausage instead. |
| Skip the meat | Leave out the sausage and add sautéed mushrooms and extra leeks for a vegetarian croissant breakfast casserole. |
How to make Croissant Breakfast Casserole
- Step 1: Cook the sausage and leeks. Brown the breakfast sausage in a skillet, breaking it into crumbles as it cooks. Add the sliced leek and cook until softened.
- Step 2: Layer the casserole. Tear the croissants into bite-size pieces and spread them in a greased 9x13-inch baking dish. Spoon the sausage and leek mixture evenly over the top.
- Step 3: Add the egg mixture. Whisk together the eggs, heavy cream, garlic powder, salt and pepper. Pour evenly over the croissants and sausage.
- Step 4: Add the cheese and chill. Sprinkle the shredded Gruyère over the casserole, cover tightly with foil and refrigerate overnight.
- Step 5: Bake. The next morning, remove the casserole from the refrigerator while the oven preheats to 375°F. Bake covered for 30 minutes, then uncover and bake another 25–30 minutes, until golden brown and set in the center.
- Step 6: Rest and serve. Let the casserole rest for about 20 minutes before slicing and serving.
Expert Tips
- Clean the leek really well. Slice it lengthwise and rinse between the layers before chopping. Dirt loves hiding in there.
- Shred your own Gruyère. It melts more smoothly than pre-shredded cheese.
- Spread everything evenly. You want sausage, leeks and custard throughout the casserole rather than one very sausage-heavy corner.
- Don't skip the overnight rest. It gives the croissants time to absorb the egg mixture and is what makes this such an easy morning-after breakfast.
- Keep it covered for the first part of baking. This helps the center cook through before you uncover it to brown and crisp the top.
- Give it time to rest after baking. About 20 minutes makes the casserole much easier to slice without losing that creamy interior.
Croissant Breakfast Casserole FAQs
An easy croissant breakfast casserole combines torn croissants with cooked breakfast sausage, leeks, eggs, heavy cream and Gruyère. Assemble it the night before, refrigerate, then bake in the morning until golden and set.
Croissants are great for savory breakfast casseroles because they soak up egg custard while staying buttery and crisp on top. They also work well in breakfast sandwiches, French toast bakes and strata-style casseroles.
Yes. Assemble the casserole completely, cover it tightly and refrigerate overnight. Bake it the next morning as directed.
No. Fresh croissants work well, but day-old croissants absorb the egg mixture especially well.
Yes. Swiss or sharp white cheddar are both good substitutes for Gruyère.
The center should be set and no longer look wet, and the top should be golden brown with crisp edges.
What to Serve with Croissant Breakfast Casserole
This casserole is pretty hearty on its own, so I like to keep the rest of brunch simple.
Serve it with fresh fruit, berries, a lightly dressed butter lettuce salad or roasted breakfast potatoes. A little hot sauce on top is also never a bad idea.
If you're putting together a bigger brunch spread, my pistachio muffins or blueberry crumb cake would give you something sweet alongside the savory casserole.
Storing and Reheating
Allow leftover croissant breakfast casserole to cool, then transfer it to an airtight container or cover the baking dish tightly.
Store leftovers in the refrigerator for up to 3-4 days.
For individual portions, reheat in the microwave until warmed through. For the best texture, loosely cover the casserole with foil and reheat it in the oven so the croissants don't get overly soft.
You can also freeze individual portions of the baked casserole. Let them cool completely, wrap well and freeze. Thaw overnight in the refrigerator before reheating.
More Easy Breakfast Casseroles
If you tried this Croissant Breakfast Casserole or any other recipe on my website, please leave a 🌟 star rating and let me know how it went in the comments below. Thanks for visiting today!
Croissant Breakfast Casserole Recipe
Ingredients
- 1 tablespoon butter
- 12 oz breakfast sausage (removed from casing, or ground)
- 1 leek- tough ends removed, cleaned halved lengthwise and sliced thinly
- 10 large eggs
- 1 ¼ cups heavy cream
- salt and fresh ground black pepper, to taste
- 1 teaspoon garlic powder
- 6 medium-large Croissants, torn into small pieces
- 6 oz gruyere cheese, shredded
Instructions
Prepping the casserole
- Melt the butter in a large nonstick skillet over medium heat.
- Add the breakfast sausage and cook, breaking it into crumbles, until browned, about 5–6 minutes.
- Add the sliced leek, season with salt and pepper, and cook for another 5–7 minutes, stirring occasionally, until softened.
- While the sausage and leeks cook, tear the croissants into bite-size pieces and arrange them evenly in a greased 9x13-inch baking dish.
- Spoon the cooked sausage and leek mixture evenly over the croissants.
- In a large bowl, whisk together the eggs, heavy cream, garlic powder, salt and pepper. Pour evenly over the croissants and sausage.
- Sprinkle the Gruyère evenly over the top. Cover tightly with foil and refrigerate overnight, or for up to 24 hours.
Baking the casserole
- When ready to bake, remove the casserole from the refrigerator and preheat the oven to 375°F.
- Bake covered for 30 minutes. Remove the foil and bake for another 20–25 minutes, until the center is set and the top is golden brown and crisp.
- Let the casserole rest for about 20 minutes before slicing and serving.
Notes
- Make ahead: Assemble the casserole, cover tightly and refrigerate overnight or for up to 24 hours before baking.
- Croissants: Fresh or day-old croissants both work well. Day-old croissants will absorb the custard especially well.
- Sausage: Use bulk breakfast sausage or sausage links with the casings removed. Mild or hot both work.
- Leeks: Clean them thoroughly before slicing, since dirt can hide between the layers.
- Cheese: Swiss or sharp white cheddar can be substituted for Gruyère.
- Doneness: The casserole is ready when the center is set and the top is golden brown.
- Storage: Refrigerate leftovers for up to 3–4 days and reheat until warmed through.
Sharon says
This is one of those breakfast casseroles I keep coming back to when I want something easy but still a little special. The buttery croissants with the sausage, leeks and Gruyère are so good, and I love that all the prep happens the night before. It’s especially great for holidays or when you have people staying over.
Heather says
This casserole was a big hit with my family. I made a couple alterations to make this non-dairy but it still worked great. Loved the idea of having the torn-up croissants on the bottom and the leeks and sausage really round out the flavor perfectly.