01 -
Turn the oven on to the broil setting. Position a rack in the middle of the oven.
02 -
In a large skillet, melt the butter and add the sausage. Break the sausage with a fork as much as you can. Cook the sausage for a minute, it doesn’t have to be completely cooked.
03 -
Add the chopped onion and mushroom to the skillet. Sauté everything for 5 minutes until the onions soften and the mushrooms begin to brown. Season the mushrooms and sausage with salt and pepper.
04 -
Pour the beaten eggs over the mushrooms and sausage in the skillet, do not stir. Cook the eggs for just a minute and sprinkle the mozzarella over the top.
05 -
Transfer the skillet to the oven and broil for a couple of minutes, just until the top is nice and golden brown. Make sure to watch it carefully because it can quickly burn.
06 -
Let the frittata cool slightly then garnish with parsley and chopped tomatoes if preferred and serve warm or at room temperature.