Preheat the oven to 375°F (190°C).
Gently clean the mushrooms and remove the stems. Finely chop the stems.
Mix the softened cream cheese, Parmesan, breadcrumbs, garlic, parsley, salt, pepper, and chopped mushroom stems in a bowl.
Lightly grease a baking dish with olive oil and arrange the mushroom caps hollow-side up.
Divide the filling evenly among the mushroom caps.
Melt the butter and drizzle it lightly over the filled mushrooms.
Bake for about 20 minutes, or until the mushrooms are tender and the filling is lightly golden.
Let the mushrooms rest for a few minutes before transferring them to a serving platter and serving warm.