A mushroom and cheddar breakfast frittata brings browned mushrooms, melted cheese, and tender eggs together in one skillet. It makes a satisfying breakfast with toast and is easy to portion for a relaxed brunch. The most useful technique is to cook the mushrooms thoroughly before adding the eggs: removing their excess moisture gives the filling a richer flavor and helps the eggs set evenly.
This recipe serves four and uses a 10-inch ovenproof skillet. You start it on the stove, then move it to the oven to finish. Sharp cheddar supplies plenty of flavor, while a little milk loosens the egg mixture without making it overly rich.
Ingredients for Mushroom and Cheddar Breakfast Frittata
- 8 large eggs
- 3 tablespoons whole milk
- 8 ounces cremini or white button mushrooms, trimmed and sliced 1/4 inch thick
- 1 small yellow onion, finely diced
- 1 tablespoon olive oil, plus a little extra if needed
- 1 tablespoon unsalted butter
- 1 small garlic clove, finely chopped
- 1 teaspoon fresh thyme leaves, or 1/4 teaspoon dried thyme
- 1 cup loosely packed grated sharp cheddar, divided
- 1/4 teaspoon fine salt, plus a small pinch for the mushrooms
- 1/4 teaspoon freshly ground black pepper
- 1 tablespoon chopped chives or parsley, for serving
You will also need a bowl, whisk, flexible spatula, and an oven mitt. Check that your skillet and its handle are suitable for a 350-degree Fahrenheit oven. A well-seasoned cast-iron skillet works well, as does an ovenproof nonstick skillet. Use utensils appropriate for its surface.
Grate the cheddar before you begin cooking and reserve about 1/3 cup for the top. Keeping the remaining ingredients ready beside the stove makes the transition from vegetables to eggs much easier.
Brown the Mushrooms Before Adding Eggs
Brush off loose dirt or wipe the mushrooms with a damp towel. If they need rinsing, rinse briefly and dry thoroughly. Slice them evenly so the pieces cook at a similar pace; very thin slices can disappear into the filling, while large chunks make tidy wedges harder to cut.
Heat the olive oil in your skillet over medium-high heat. Add the mushrooms and spread them into a fairly even layer. Leave them alone for about two minutes before stirring. Continue cooking for another four to six minutes, stirring occasionally, until their released liquid has evaporated and the edges begin to brown.
Watch the pan rather than relying entirely on the clock. The mushrooms should look smaller and lightly golden, with no puddle underneath. If the skillet is crowded, work in two batches so the mushrooms have space to brown. Season with a small pinch of salt, then transfer them to a plate.
Removing the mushrooms lets you soften the onion without keeping the browned slices over the heat the entire time. Leave any flavorful brown residue in the skillet, provided it has not burned.
Make the Frittata Step by Step
- Preheat the oven. Set it to 350 degrees Fahrenheit and place a rack in the middle. Keep a clear heatproof space ready for the hot skillet when it comes out.
- Soften the onion. Reduce the stovetop heat to medium-low and add the butter to the skillet. Stir in the diced onion and cook for five to seven minutes, stirring occasionally, until soft. Add the garlic and thyme and cook for about 30 seconds, until fragrant.
- Whisk the eggs. In a bowl, whisk the eggs, milk, measured salt, and pepper until the whites and yolks are blended. Avoid beating in a thick layer of foam. Stir in the larger portion of the cheddar.
- Distribute the vegetables. Return the mushrooms to the skillet and stir them through the onion. Spread the filling evenly across the bottom. If the exposed sides look dry, brush them with a little extra oil.
- Add the egg mixture. Pour it evenly over the vegetables. Gently move any large clumps of mushrooms with the spatula so each wedge will contain some filling. Cook over medium-low heat for two to three minutes, until a narrow band of egg starts setting around the edge.
- Finish in the oven. Sprinkle the reserved cheddar over the top. Transfer the skillet to the oven and bake for approximately 12 to 16 minutes. Begin checking early, since the pan and oven affect the timing. The center should be set, without a glossy pool of uncooked egg.
- Rest before slicing. Put the skillet on the prepared heatproof surface and rest for five minutes. Add the chopped herbs, loosen the edge gently, and cut into wedges. Leave an oven mitt over the handle to remind everyone that it remains hot.
Keep the Texture Tender
Gentle heat is the main safeguard against rubbery eggs. The stovetop stage establishes the base, while the oven finishes the center. Do not wait for most of the eggs to set on the stove before transferring the skillet, because the bottom can become tough while the top is still loose.
Check the center with a gentle nudge of the pan. It should move as a cohesive piece rather than slosh beneath the cheese. If you cannot tell, make a small cut near the middle to check for liquid egg, then return it to the oven briefly if needed.
A deeply browned top is unnecessary. Once the eggs are set, take the frittata out and let it rest. Leaving it in the switched-off oven while you prepare other dishes can continue cooking the eggs and make the edges firmer.
Easy Ingredient Adjustments
Choose your mushrooms
Cremini mushrooms give a savory flavor that stands up well to cheddar. White button mushrooms produce a milder filling. For variety, replace part of the quantity with sliced shiitakes, removing their tough stems first. Keep the total quantity similar and cook away the moisture before proceeding.
Add a little spinach
A small handful of baby spinach fits comfortably into this recipe. Wilt it with the softened onion and let any released water evaporate before returning the mushrooms. Adding a large pile of raw greens with the eggs can create wet pockets and disturb the balance of filling to egg.
Change the herbs
Chives add a gentle onion flavor at the table, while parsley gives a fresh finish. A little chopped oregano can replace the thyme. Use stronger herbs sparingly so their flavor supports the mushrooms and cheddar.
Bring Breakfast Together
Serve the wedges with buttered wholegrain toast and sliced tomatoes, or add fresh fruit alongside. A lightly dressed handful of leaves also works well if you are serving the frittata later in the morning.
To simplify preparation, slice the mushrooms, dice the onion, and grate the cheese ahead, keeping them covered in the refrigerator. Cook the frittata when you are ready to eat. While it bakes, set out plates and prepare your accompaniments; use the short resting time to finish the toast and scatter the herbs.
