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This hearty spinach mushroom breakfast casserole has been my weekend brunch solution for years. Packed with protein and veggies, it's become my go-to recipe whenever I host morning gatherings or need to meal prep for busy weekdays.
I first made this casserole when my in-laws visited unexpectedly one Sunday morning. Everyone raved about it, and now it's requested at every family gathering. The combination of earthy mushrooms and tangy goat cheese creates a flavor profile that even vegetable skeptics enjoy.
Ingredients
- Olive oil: adds a subtle richness when sautéing the vegetables
- Cremini mushrooms: provide meaty texture and umami flavor; choose firm ones with tight caps
- Spinach leaves: fresh spinach wilts perfectly and provides essential nutrients
- Garlic: fresh minced cloves offer more flavor than pre-minced varieties
- Kosher salt and black pepper: essential for balancing and enhancing all flavors
- Green onions: add a mild onion flavor without overpowering the dish
- Goat cheese: creates pockets of creamy tanginess throughout the casserole
- Large eggs: form the protein-rich base; look for pasture-raised for best flavor
- Milk: helps create a custard-like texture; whole milk works best but any variety works
- Fresh chives (optional): adds bright color and mild flavor as garnish
Step-by-Step Instructions
- Prep Your Baking Dish:
- Preheat oven to 350 degrees Fahrenheit and thoroughly grease a 9×13 inch baking dish with nonstick spray. Make sure to cover the corners and sides completely to prevent sticking since eggs tend to cling to ungreased surfaces.
- Sauté The Vegetables:
- Heat olive oil in a large skillet over high heat until shimmering. Add sliced mushrooms in a single layer if possible and cook undisturbed for about a minute before stirring. Continue cooking for about 2 more minutes until they release their moisture and become tender. Add spinach and minced garlic, then cook for another 3 minutes, stirring frequently until spinach is completely wilted but still bright green. Season mixture with salt and pepper to enhance the natural flavors.
- Layer The Base:
- Transfer the cooked vegetable mixture to your prepared baking dish, spreading it evenly across the bottom. Sprinkle the sliced green onions over the vegetables, distributing them uniformly. Take half of your goat cheese and crumble it over the vegetables in small pieces to ensure pockets of cheese throughout the casserole.
- Prepare And Add Egg Mixture:
- In a large bowl, crack 18 eggs and add the milk. Whisk vigorously until completely combined and slightly frothy. Season the egg mixture with salt and pepper. Pour this mixture slowly over the vegetable and cheese layer, allowing it to settle evenly. Crumble the remaining goat cheese over the top, creating an attractive pattern.
- Bake To Perfection:
- Place the casserole in the preheated oven and bake for 30 to 40 minutes. You'll know it's done when the eggs are completely set and the edges have a slight golden brown color. The center should be firm but still moist when lightly touched. Allow to rest for 5 minutes before garnishing with fresh chives and cutting into squares.
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The cremini mushrooms are truly the star of this casserole. I discovered their rich flavor after years of using button mushrooms, and the difference is remarkable. When my daughter was younger, she would pick them out, but now she requests extra mushrooms whenever I make this dish for our Sunday brunches.
Make Ahead Magic
This casserole excels as a make-ahead option. You can prepare the entire casserole up to the baking step, cover tightly with plastic wrap, and refrigerate overnight. When ready to serve, remove from the refrigerator 30 minutes before baking to take the chill off, then bake as directed, adding about 5 extra minutes to the cooking time. For busy holiday mornings or when hosting brunch, this time-saving technique is invaluable.
Storage Solutions
Once cooled, leftover casserole can be refrigerated for up to 4 days in an airtight container. For individual portions, cut the casserole into squares and store them separately for grab-and-go breakfasts during the week. To reheat, microwave individual portions for about 60 seconds or warm in a 325°F oven until heated through. This casserole also freezes beautifully for up to 3 months; wrap individual pieces tightly in plastic wrap, then foil, and defrost overnight in the refrigerator before reheating.
Clever Substitutions
This recipe welcomes adaptations based on what you have available. Swiss chard or kale can replace spinach; use the same amount but remove tough stems first. Feta cheese creates a saltier profile than goat cheese, while cream cheese offers a milder flavor. Any variety of mushrooms works wonderfully—portobello, shiitake, or white button mushrooms all bring their unique character to the dish. For a dairy-free version, substitute unsweetened almond milk and omit the cheese or use a plant-based alternative.
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Serving Suggestions
This casserole pairs beautifully with a variety of sides. Serve with toasted sourdough bread and fresh fruit for a complete breakfast spread. For brunch gatherings, offer it alongside a simple arugula salad dressed with lemon vinaigrette to cut through the richness. During cooler months, a side of roasted breakfast potatoes complements the casserole perfectly. For a lighter option, serve smaller portions with avocado slices and fresh tomatoes drizzled with olive oil.
Frequently Asked Questions
- → Can I use other types of mushrooms?
Yes, you can substitute cremini mushrooms with button mushrooms, shiitake, or portobello for a slightly different flavor.
- → How can I make this casserole dairy-free?
To make it dairy-free, replace goat cheese with a dairy-free cheese alternative and use plant-based milk like almond or oat milk.
- → Can I prepare this dish in advance?
Yes, you can assemble the casserole the night before and refrigerate. Bake it fresh in the morning for best results.
- → What’s a good side dish to pair with this?
This casserole pairs well with fresh fruit, toast, or a light salad for a rounded breakfast or brunch menu.
- → Can I freeze leftovers?
Yes, let the casserole cool completely, cut it into portions, and store in an airtight container in the freezer for up to 3 months. Reheat before serving.
- → What herbs can I use for garnish?
Chopped chives, parsley, or even fresh dill work wonderfully as garnishes for added flavor and color.