The moment the pan hit the heat, the aroma was enough to pull everyone into the kitchen. As the sausage sizzled and the onions caramelized, the promise of a savory breakfast casserole filled with rich, gooey cheese and hearty bread began to take shape. This festive dish is not just a meal; it’s a celebration that brings family and friends together, making mornings feel a little more special, especially around the holidays.
What makes this recipe shine
What sets apart this breakfast casserole is its perfect blend of flavors and textures. The richness of the eggs and cream creates a silky custard that envelops the crusty sourdough, while the robust sausage and melty cheeses add depth that leaves your taste buds singing. It’s simple yet luxurious, and you can easily customize it based on what you have at home or your personal preferences. As one reader put it:
“This casserole is a crowd-pleaser that’s easy to prepare and simply unforgettable!”
How this dish comes together
Creating this Christmas breakfast casserole is a straightforward process with minimal fuss. You’ll start by browning the sausage and onion to build a savory base. Once they’re perfectly browned, you’ll mix them with the bread and cheese, creating a hearty blend that forms the backbone of the dish. The magic happens when you pour the creamy custard over it all, allowing every morsel to soak up delicious flavors. With a little patience—refrigerating overnight for the best results—you’ll soon be ready to bake up a masterpiece.
What you’ll need
Gather the following ingredients to whip up this delightful casserole:
- 1 lb pork breakfast sausage
- 1 large yellow onion, chopped
- 1 (1-pound) loaf of sourdough bread, cut into 1-inch cubes
- 2 cups shredded Gruyère cheese
- 1/2 cup grated Parmesan cheese
- 8 large eggs
- 2 cups whole milk
- 1 cup heavy cream
- 1 tbsp Dijon mustard
- 1 tsp salt
- 1/2 tsp black pepper
- 1/4 tsp ground nutmeg
When selecting your ingredients, aim for high-quality sausage and fresh bread to elevate the flavor. For a lighter option, consider substituting turkey sausage or whole grain bread.
Step-by-step cooking
In a large skillet over medium heat, cook the pork sausage and chopped onion until the sausage is browned and the onion is soft, about 6-8 minutes. Make sure to drain excess grease to keep the casserole from becoming too oily.
In a spacious bowl, combine the bread cubes, the sautéed sausage and onion mixture, and the shredded Gruyère and Parmesan cheeses. Stir well to ensure the bread absorbs all those luscious flavors.
In the same bowl, whisk together the eggs, whole milk, heavy cream, Dijon mustard, salt, black pepper, and nutmeg until smoothly blended.
Pour the custard evenly over the bread mixture, pressing down lightly to help the bread soak up the egg mixture.
Transfer everything to a greased 9×13-inch baking dish, cover with plastic wrap, and refrigerate overnight or at least for 8 hours.
Preheat your oven to 350°F (175°C). Before baking, allow the casserole to sit at room temperature for about 30 minutes to take the chill off.
Bake the casserole uncovered for 50-60 minutes, or until it’s golden brown and set in the middle. Let it rest for 10 minutes before serving to let the flavors settle.

Serving ideas
When it’s time to serve, slice your casserole into generous squares and place them on warm plates. A sprinkle of fresh chopped herbs, like parsley or chives, can add a final touch of color and freshness. Pair it with a bright side salad or some seasonal fruit to balance the richness. This casserole is hearty enough that it can stand alone, but a splash of hot sauce or a dollop of crème fraîche on top can really elevate the flavors.
Keeping leftovers fresh
Once your guests have enjoyed this fabulous dish, you might find yourself with leftovers. Store any remaining casserole in an airtight container in the refrigerator for up to three days. For longer storage, you can freeze portions for up to two months. When you’re ready to enjoy again, reheat in a 350°F (175°C) oven until warmed through, which helps retain that delicious texture.
Helpful cooking tips
For an extra depth of flavor, consider sautéing added veggies like bell peppers or spinach along with the sausage and onion.
If you want to add a little kick, sprinkle in some red pepper flakes or diced jalapeños when cooking the sausage.
To ensure a perfectly custardy texture, make sure to let the casserole soak overnight. This will help the bread absorb that rich custard.
Use day-old bread for better structure; it absorbs more liquid without becoming mushy.
If you’re short on time, you can prepare it in the morning and bake it in the evening, but letting it sit overnight yields the best results.
Ways to customize it
Feel free to put your spin on this casserole! Switch up the cheese with cheddar or mozzarella for different flavor profiles. You can also substitute cooked bacon or ham for the sausage, or try adding seasonal vegetables like zucchini or mushrooms for a healthier option. During the holiday season, consider adding a sprinkle of cranberry or chopped pecans for sweetness and crunch.
Frequently Asked Questions
Will I be able to prepare this casserole in advance?
Absolutely! The casserole benefits from soaking overnight, allowing the bread to fully absorb the custard.
Can I use low-fat milk instead of whole milk?
Yes, but keep in mind that it may affect the creaminess of the final dish. Using whole milk and heavy cream produces the richest texture.
How do I ensure the casserole doesn’t get too dry?
It’s essential to follow the soaking time to ensure the bread is fully saturated. If it looks dry after baking, you can drizzle some warm cream over the top before serving.


Savory Breakfast Casserole
A hearty breakfast casserole with sausage, cheese, and crusty bread, perfect for gatherings.
- Total Time: 75 minutes
- Yield: 8 servings 1x
Ingredients
- 1 lb pork breakfast sausage
- 1 large yellow onion, chopped
- 1 (1-pound) loaf of sourdough bread, cut into 1-inch cubes
- 2 cups shredded Gruyère cheese
- 1/2 cup grated Parmesan cheese
- 8 large eggs
- 2 cups whole milk
- 1 cup heavy cream
- 1 tbsp Dijon mustard
- 1 tsp salt
- 1/2 tsp black pepper
- 1/4 tsp ground nutmeg
Instructions
- In a large skillet over medium heat, cook the pork sausage and chopped onion until browned, about 6-8 minutes; drain excess grease.
- In a bowl, combine bread cubes, sautéed sausage and onion, and cheeses; stir well.
- Whisk together eggs, whole milk, heavy cream, Dijon mustard, salt, black pepper, and nutmeg until smooth.
- Pour custard over bread mixture and press down lightly.
- Transfer to a greased 9×13-inch baking dish, cover, and refrigerate overnight or for 8 hours.
- Preheat the oven to 350°F (175°C). Allow casserole to sit at room temperature for 30 minutes.
- Bake uncovered for 50-60 minutes until golden brown and set. Let rest for 10 minutes before serving.
Notes
Store leftovers in an airtight container in the refrigerator for up to three days; freeze portions for longer storage.
- Prep Time: 15 minutes
- Cook Time: 60 minutes
- Category: Breakfast
- Method: Baking
- Cuisine: American
- Diet: Gluten-Free Option
Nutrition
- Serving Size: 1 serving
- Calories: 450
- Sugar: 5g
- Sodium: 800mg
- Fat: 30g
- Saturated Fat: 15g
- Unsaturated Fat: 10g
- Trans Fat: 0g
- Carbohydrates: 35g
- Fiber: 2g
- Protein: 20g
- Cholesterol: 150mg



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