This Savory Mushroom and Spinach Breakfast Casserole is a cozy, satisfying start to your day — perfect for lazy weekends or when you want to impress brunch guests. It's packed with hearty mushrooms, fresh spinach, and a touch of nutmeg that brings everything together wonderfully.
Mushrooms add a savory depth to the casserole. I love using button mushrooms for their mild flavor and texture, but feel free to experiment with your favorite variety.
Olive oil is used for sautéing, bringing out the natural sweetness of the onions and garlic.
Onion and garlic form the aromatic base, adding layers of flavor that make this dish irresistible.
Spinach introduces a fresh, slightly earthy note, complementing the richness of the mushrooms and cheese.
Eggs and milk create a creamy, custard-like texture that holds everything together beautifully.
Cheddar cheese offers a sharp, tangy richness, while Parmesan adds a nutty, salty finish.
Whole wheat bread cubes soak up the egg mixture, providing structure and a subtle nuttiness from the grains.
Nutmeg is the secret ingredient, adding a warm complexity that elevates the overall flavor profile.
This casserole pairs beautifully with a simple arugula salad dressed with lemon vinaigrette. The peppery greens and bright dressing complement the savory richness of the casserole. It's also fantastic served alongside some fresh fruit or a scoop of yogurt for a well-rounded breakfast.
Start by preheating your oven to 350°F and greasing an 8x8 inch baking dish with a bit of oil or butter. This ensures your casserole will come out easily and have a lovely, golden crust.
Heat a tablespoon of olive oil in a skillet over medium heat. Add the chopped onions and minced garlic, sautéing them until they're soft and fragrant. This usually takes about 3–4 minutes. The aroma will fill your kitchen and set the stage for the flavors to come.
Next, toss in the sliced mushrooms. Cook them until they release their moisture and start to brown slightly, which should take another 5 minutes or so. Stir occasionally to ensure even cooking.
Once the mushrooms are ready, add the chopped spinach to the skillet. Stir it around until it wilts, then remove the skillet from the heat. This quick wilting keeps the spinach vibrant and fresh-tasting.
In a large mixing bowl, whisk together the eggs, milk, salt, pepper, and a pinch of nutmeg. The nutmeg is subtle but makes a big difference in flavor, so don't skip it!
Add the bread cubes, sautéed vegetables, cheddar, and Parmesan to the egg mixture. Stir everything together until it's well combined. Make sure the bread is evenly coated with the egg mixture for the best texture.
Pour this mixture into your prepared baking dish, spreading it out evenly. Pop it in the oven and bake for 35-40 minutes until the top is golden brown and the casserole is set. Your kitchen will smell amazing!
Once baked, let the casserole cool for a few minutes before slicing and serving. This brief rest helps the flavors meld and makes it easier to cut clean pieces.
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