Serious Eats / Fred Hardy

Why It Works

• Sautéeing the sausage and vegetables before adding them to the casserole ensures they’re fully cooked and removes excess moisture.
• Adding shredded Gouda cheese, sour cream, and half-in-half to the eggs creates a rich custard-like filling.

Savory, hearty, and packed with flavor, a well-made breakfast casserole is great for feeding a crowd. The ideal breakfast casserole should be creamy and packed with flavorful add-ins, and easy to slice into neat portions. Unfortunately, I have had some seriously bad egg casseroles in my past—ones that are so overcooked and rubbery, you could fling them across the room like a frisbee. That’s why I appreciate a really good recipe for breakfast casserole, like this one from our Birmingham-based test kitchen colleague Elizabeth Mervosh.

Mervosh baked up countless casseroles to created this flavorful egg, vegetable, cheese, and sausage version that’s sure to impress everyone at your next family gathering or brunch. She gussies up her casserole with a thoughtful combination of ingredients like Italian sausage, earthy mushrooms, bright sun-dried tomatoes, garlic, onion, and heaps of fresh spinach. It’s all folded with shredded melty cheese (Gouda or cheddar) before being combined with the eggs and baked.

The casserole is easy to make and can be prepared ahead of time, so you don’t have to wake up at the break of dawn just to get breakfast on the table. Here are a few tips for a savory breakfast casserole that’s extremely satisfying, not soggy, greasy, or underseasoned.

Serious Eats / Fred Hardy

4 Important Steps to Guarantee a Great Savory Breakfast Casserole

1. Pre-cook the sausage and vegetables. Eggs cook quickly—far too fast for fillings to do much beyond warm up a bit by the time the eggs are fully cooked. So the key to a great sausage- and vegetable-loaded egg casserole is to cook your fillings beforehand. We start by cooking the sausage, then set it aside before sautéeing the mushrooms and onions in the rendered sausage fat—this fat and and the fond left behind in the skillet from the sausage imbue the mushrooms and onions with porky, salty flavor. The other aromatics and vegetables, including sun-dried tomatoes, garlic, and fresh spinach, are added after the mushrooms and onions. Sautéing the sausage and vegetables not only makes them tender and helps them develop a robust flavor, but cooking the fillings drives off excess moisture, ensuring a creamy— not watery—casserole.

2. Load up on the dairy. It can be challenging to ensure baked eggs in a large casserole dish are evenly cooked from edge to edge. The eggs can easily overcook and turn rubbery. To ensure the eggs remain tender once baked, we whisked a hearty amount of half-and-half (or whole milk, if you prefer) and sour cream into the egg mixture until fully combined. The added fat from the dairy results in a creamier custard-like filling.

3. Make it easier by building it right in the casserole dish. We wanted to make this casserole as easy as possible to prepare without sacrificing flavor. That’s why we don’t skip sautéing the add-ins as described above—the time savings are just not worth it. But one shortcut we do encourage is skipping the mixing bowl and simply combining all the casserole ingredients directly in the baking dish so there’s one less bowl to clean up.

**4. Customize it. **This egg casserole is easily adaptable, so feel free to try out your favorite add-ins or swaps. You can omit the pork sausage entirely or swap it for turkey or veggie sausage. Any cheese that shreds and melts easily, such as Gruyère or Monterey Jack, will also work well here. Kale can be swapped in for the spinach and tomatoes can be added as well (just be sure to cook these ingredients first to remove excess moisture, just like you would with the spinach). To make it heartier, fold in some roasted potatoes, sweet potatoes, or root vegetables. (Leftover cooked vegetables work well too.) Get creative and remember that beyond breakfast this savory egg dish also makes a wonderful lunch or dinner.

The recipe was developed by Elizabeth Mervosh; the headnote was written by Leah Colins.

October, 2024

Keep Screen Awake

2 tablespoons extra-virgin olive oil, plus more as needed

12 ounces (340g) bulk sweet or hot Italian sausage (optional)

5 ounces (140g) thinly sliced fresh mushrooms, such as shiitake, cremini, or oyster (2 cups sliced)

1 small red onion (6 ounces; 170g), thinly sliced (about 1 cup sliced)

1 1/2 teaspoon Diamond Crystal kosher salt, divided; for table salt use half as much by volume

1/2 cup drained and chopped sundried tomatoes in oil (3 ounces; 85g)

3 medium garlic cloves, minced

5 ounces (140g) fresh baby spinach (5 cups)

6 ounces (170g) shredded Gouda or cheddar cheese, (1 1/2 cups)

10 large eggs

1/3 cup (80ml) sour cream or plain, whole-milk strained (Greek-style) yogurt

1 1/2 cups (360ml) half-and-half or whole milk

1 tablespoon (15ml) Dijon mustard

Adjust oven rack to middle position and preheat oven to 350°F (175℃). Lightly grease a 9- x 13-inch baking dish with oil; set aside. If using sausage, in a 12-inch skillet, heat 1 tablespoon oil over medium-high until shimmering. Add sausage and using a wooden spoon, break it into large clumps. Continue to cook without moving until browned on bottom, about 4 minutes. Use wooden spoon to break up meat into smaller pieces and continue to cook, stirring occasionally, until sausage is just cooked through, about 3 minutes. Using a slotted spoon, transfer sausage to a paper towel–lined plate. Reserve 2 tablespoons rendered fat in skillet to cook mushrooms.

Serious Eats / Fred Hardy 1.

Heat rendered fat in skillet (or if omitting sausage, heat 2 tablespoons oil in 12-inch skillet) over medium-high heat until shimmering. Add mushrooms, stir to coat in oil, and spread in an even layer. Cook without moving until bottoms of mushrooms are browned, about 4 minutes. Reduce heat to medium. Add onion, 1/2 teaspoon salt, and 1 tablespoon oil. Cook, stirring occasionally, until onions soften and mushrooms are browned all over, about 8 minutes.

Serious Eats / Fred Hardy 1.

Add sundried tomatoes and garlic; cook, stirring often, until fragrant, about 1 minute. Add spinach in 2 additions, stirring often and letting spinach completely wilt before adding more. Transfer vegetable mixture, and sausage (if using), to prepared baking dish. Stir in cheese until combined, and spread mixture in an even layer.

Serious Eats / Fred Hardy 1.

In a large bowl, whisk eggs until no streaks remain. Whisk in sour cream in 3 additions until no lumps remain. Whisk in half-and-half, mustard, and remaining 1 teaspoon salt until combined. Pour egg mixture over mushroom mixture in baking dish; gently stir until egg mixture is evenly distributed.

Serious Eats / Fred Hardy 1.

Bake, uncovered, until cooked through, puffed and set, about 35 minutes. Let cool 10 minutes. Slice and serve.

Serious Eats / Fred Hardy

Special Equipment

9- x- 13-inch baking dish, 12-inch skillet

Make-Ahead and Storage

To prepare the recipe ahead, cook as directed through Step 3. Cover with plastic wrap and refrigerate for up to 24 hours. Let the casserole sit at room temperature while the oven preheats; remove plastic wrap, stir to thoroughly recombine, and proceed with Step 4 as directed.

The casserole can be baked ahead, cooled to room temperature and refrigerated, covered, for up to 2 days. It can also be frozen for up to 2 months. To reheat, bring to room temperature before heating, covered with aluminum foil, in a 350°F (175℃) oven until warmed through.

Nutrition Facts (per serving)
481	Calories
37g	Fat
14g	Carbs
25g	Protein

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Nutrition Facts Servings: 8 Amount per serving Calories 481 % Daily Value* 37g 47% Saturated Fat 15g 76% 300mg 100% 907mg 39% 14g 5% Dietary Fiber 2g 8% Total Sugars 6g 25g Vitamin C 20mg 99% Calcium 291mg 22% Iron 3mg 17% Potassium 716mg 15% *The % Daily Value (DV) tells you how much a nutrient in a food serving contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.

(Nutrition information is calculated using an ingredient database and should be considered an estimate.)