In a saute pan over medium heat, brown the sausage until it is no longer pink with the salt, pepper, onion, and garlic. Drain any excess grease. (High-quality loose sausage should not create a lot of excess oil. And prevents your dip from being oily.)
Turn the heat to medium-low heat, add the cream cheese and sour cream to the browned sausage.
Stir regularly the mixture for 5 minutes.
Add the oregano and a half cup of mozzarella cheese, and stir for another 3 minutes.
Pour the dip into a bowl and garnish with the mozzarella cheese and parsley.