Wash mushrooms and carefully take off the stems. Toss mushroom caps lightly in olive oil and set aside. (Save stems.)
Preheat a medium cooking pan over medium heat, add a little oil and cook sausage, breaking it apart as much as possible.
Dice mushroom stems and add them to the sausage about half way through cooking. Cook until sausage is done.
In a mixing bowl, combine cooked sausage, cream cheese, pressed garlic, parsley, salt, pepper, and Mozzarella cheese and mix until all is evenly incorporated.
Stuff each mushroom cap with some of the filling, pressing it in gently and add enough to have a dome on top.
Place mushroom caps in a lightly greased baking dish.
Sprinkle with a little more cheese and parsley on top and bake for 20-22 minutes. (Time will slightly depend on the size of mushrooms by 2-4 minutes.)