This delightful Breakfast Casserole is layered with earthy mushrooms, onions, peppers, potatoes, baby spinach, fluffy eggs and melty, gooey cheese. Serve this make-ahead casserole for breakfast, brunch or even dinner with a green salad on the side. It serves 6 as a main dish and 10 to 12 as a side.
Prep Time30 minutesmins
Cook Time50 minutesmins
Total Time1 hourhr20 minutesmins
Servings: 6as a main
Ingredients
4slicesthick-cut bacon, cut crosswise into 1/2-inch pieces
8ouncescremini mushroomsthinly sliced
1large yellow onionthinly sliced
1teaspoonolive oil (only if needed)
3garlic clovesminced
Kosher salt and freshly cracked black pepper
2bell peppersdiced (I use red peppers)
3cupsfresh baby spinach
4cupsfrozen shredded, or diced, potatoes* (do not thaw)
1 1/4cupshredded cheddar cheese,divided
12large eggs
2/3cup(160ml) milk or half-and-half*
optional garnish: chopped dill and/or chives
Instructions
Arrange a rack in the middle of the oven and heat to 375°F. Coat a 9x13-inch baking dish with baking spray or olive oil; set aside.
In a large skillet, cook the bacon over medium heat, stirring occasionally, until browned and crisp. Using a slotted spoon, transfer bacon to a plate lined with paper towels; set aside.
Remove all but 1 tablespoon of bacon fat from the skillet and heat over medium-high heat.
Add the mushrooms and cook, undisturbed for 2 minutes. Give them a toss and cook for another 2 minutes. Lower the heat to medium, add the teaspoon of olive oil if skillet seems dry, then add the onions, garlic, and 1/2 teaspoon of salt. Cook, stirring occasionally, until onions are translucent, about 3 minutes. Stir in the peppers and cook, stirring occasionally, for about 1 minute. Add in the spinach and once wilted, remove from heat. Stir in the frozen shredded (or diced) potatoes and toss with all the veggies.
Transfer vegetable mixture to prepared baking dish and spread into an even layer. Sprinkle cooked bacon and 1 cup cheese evenly over top.
In a large bowl, whisk the eggs, milk, 1 teaspoon salt and pepper to taste. Pour over the vegetables. Sprinkle remaining cheese evenly over the top.
Bake the casserole, uncovered, until edges are golden brown and the casserole has puffed up beautifully, 45 to 55 minutes. (The tip of a knife inserted in the middle should come out clean.) Let sit for 5 or 10 minutes. Garnish with fresh herbs, if using, then slice and serve hot.
Notes
Potatoes - For convenience, here we use shredded or diced frozen hash brown potatoes. No need to thaw them. However, especially around the holidays, they're sometimes hard to find. If you need to use fresh potatoes, like I did when I photographed this recipe, here's what to do: Substitute one small/medium potato for each cup of frozen potatoes. Prick each potato several times with a fork, then place in the microwave on a paper towel. Microwave on HIGH for 8 to 10 minutes, or until the potatoes are just barely tender. Once cool enough to handle, peel the potatoes and shred on a box grater. You can also dice the potatoes, if you prefer.
Milk - You can use whole milk in this casserole but half-and-half adds a luxurious richness to the dish.
Make Ahead: The casserole can be completely assembled, covered tightly with plastic wrap or aluminum foil, and refrigerated overnight (but no longer) before baking. Uncover before baking and add a few extra minutes of baking time.
To Store: Refrigerate leftovers in an airtight storage container for up to 3 days.
To Reheat. Reheat leftovers in a baking dish, in a preheated 350ºF oven until warmed through.