Preheat the oven to 375 degrees F and line a baking sheet with parchment paper.
Wipe the mushrooms clean with a damp cloth, then twist off the stems and set the caps aside.
Finely chop the mushroom stems and place them in a mixing bowl with the Parmesan cheese, cream cheese, minced garlic, parsley, salt, and black pepper. Stir until the mixture forms a thick paste.
Spoon the filling into each mushroom cap, pressing gently to fill them evenly.
Arrange the stuffed mushrooms on the baking sheet and drizzle the olive oil over the tops.
Bake for 20 minutes until the mushrooms soften and the filling turns lightly golden on the edges. Let them cool for a few minutes before serving.