Prepare the Mushrooms: Preheat the oven to 375°F (190°C). Gently wipe the mushrooms clean with a damp paper towel. Remove the stems and set the mushroom caps aside. Finely chop the stems for the filling.
Season the Mushroom Caps: Arrange the mushroom caps hollow-side up on a baking sheet or in a baking dish. Brush them lightly with olive oil and season with a small pinch of salt and black pepper.
Make the Cream Cheese Filling: In a mixing bowl, combine the softened cream cheese, Parmesan, 2 tablespoons of breadcrumbs, minced garlic, chopped mushroom stems, parsley, Italian seasoning, salt, and black pepper. Mix until creamy and evenly combined.
Stuff the Mushrooms: Spoon the cream cheese mixture into each mushroom cap, filling it generously without letting the mixture spill over the sides. Smooth the tops with the back of a spoon.
Prepare the Topping: Combine the melted butter with the additional tablespoon of breadcrumbs. Sprinkle a little over each stuffed mushroom for a lightly crisp finish.
Bake Until Tender: Place the baking sheet in the preheated oven and bake for 20–25 minutes, until the mushrooms are tender and the filling is hot with lightly golden tops.
Brown the Tops: If you prefer a more golden finish, switch the oven to broil for the final 1–2 minutes. Watch closely to prevent the breadcrumbs from burning.
Rest and Serve: Allow the mushrooms to cool for 3–5 minutes before serving. Garnish with extra chopped parsley and serve warm.