Preheat your oven to 375°F (190°C).

Gently clean the mushrooms with a damp cloth and remove the stems, finely chopping them for the filling.

In a mixing bowl, combine the chopped mushroom stems with cream cheese, sausage (or bacon), Parmesan, garlic, parsley, salt, and pepper. Mix well to form a smooth filling.

Fill each mushroom cap with the prepared filling, heaping it slightly above the rim.

Press a small olive into the center of each stuffed mushroom.

Arrange the stuffed mushrooms on a greased baking sheet. Bake for 20-25 minutes until tender and bubbly.

Remove from the oven and allow to cool slightly before serving on a platter, garnished with parsley if desired.