Sauté sausage, peppers, onions and mushrooms seasoned with garlic and oregano.
Whisk 2 eggs in a bowl.
Melt butter in an omelet pan at medium heat.
Pour in egg mix, and when it starts to get firm on the bottom, use a spatula to pull uncooked portion to the center of the pan, allowing uncooked eggs to run back out to the edge. Do not fold, as omelet will be served open faced as a frittata.
Spread Mozzarella cheese over omelet.
Then spread pizza sauce over cheese.
Break up sausage and scatter it with other ingredients over entire omelet.
Shake omelet pan to loosen omelet and spill out onto plate in one motion or cut into shaped servings and serve from pan.