Sausage mushroom frittata is a hearty baked egg dish made with savory Italian sausage, sautéed mushrooms, and leeks folded into fluffy eggs with melty Swiss cheese.
Preheat the oven to 375°F. In a bowl, whisk together the eggs and milk until well combined.
In a large oven-safe skillet over medium heat, cook the Italian sausage, breaking it up as it browns. Add the sliced mushrooms and leek and cook until the mushrooms are softened and the leek is tender.
Pour the egg mixture into the skillet and stir gently to evenly distribute the sausage and vegetables.
Sprinkle the Swiss cheese evenly over the top.
Cook for 2 to 3 minutes, just until the edges start to set, then transfer the skillet to the oven.
Bake for 20 minutes, or until the center is set and no longer jiggly. Let rest for a few minutes, then slice and serve.