This garlicky baby bella mushroom and Gruyère cheese frittata is a nutty, savory all-star meal that's perfect any time of day!
Preheat oven to 350°F. In a large bowl, crack all 12 eggs and whisk together with milk, 1/2 tsp kosher salt and 1/4 tsp pepper. Set aside. Grate 1/4 of the cheese, chop the remaining cheese into 1/4 inch cubes and set aside.
Heat butter and olive oil in a 12-inch nonstick oven safe skillet over medium-high heat. When butter is melted, add mushrooms, onions, garlic, 1/2 tsp kosher salt and 1/4 tsp pepper and sauté until mushrooms and onion are tender and slightly browned and all the liquid from the mushrooms has been released and cooked off, about 7-8 minutes.
Add egg mixture and use a rubber spatula to constantly stir and scrape the bottom of the pan until large curds form and the spatula leaves a visible trail through the egg mixture but the eggs are still very wet, about 2 minutes. Stir in cubed cheese. Use the rubber spatula to spread the egg mixture evenly into the pan, flattening the top and tucking down the sides into a disc shape.
Top with grated cheese and transfer to the oven. Bake until the eggs are cooked on top, the frittata is slightly puffed and bounces back when touched, about 6 minutes.
If you like the cheese on top to be softer and have a meltier texture, carefully (!) remove from oven now and allow frittata to cool in the pan for about 5 minutes. If you like the cheese on top to be crispier with a little bit of browning, switch the oven to broil and place the pan under the broiler for about 2 minutes, until cheese is bubbling and lightly browned. Carefully (!) remove from oven and allow to cool in the pan for about 3 minutes.
Use a rubber spatula to loosen the sides and bottom of the frittata from the pan and slide it onto a cutting board. Cut into desired number of wedges (I usually do 8) and serve!
Be SO SO CAREFUL not to touch the handle of the pan after you take it out of the oven - it's so easy to forget that it just came out of the oven and then grab it & burn your hand. I recommend keeping the handle covered with a kitchen towel or potholder after you take it out to remind yourself (and everyone else!) that the handle is hot.
Mushroom and Gruyère Frittata https://yummynoises.com/mushroom-and-gruyere-frittata/