Start by grating the sausages.
Into a bowl, add the eggs, beat them well, add the milk and mix again.
Add the grated sausages and mix well until combined.
To season, add the salt, the black pepper and some parsley to taste. Mix it all together very well again. Set aside.
Into a skillet, add some olive oil and spread well. Transfer all the sausage mixture to the skillet and spread it out.
Close the skillet and let it all cook for 5 minutes over very low heat. After this time, flip the omelet, cover it with the mozzarella cheese, close the skillet again and let it all cook for another 2 minutes, until the other side also cooks through and the cheese melts.
After this indicated time, take it out of the skillet and serve.