Preheat oven to 400 F. Line a rimmed baking sheet with parchment paper, and set aside.
In a medium size mixing bowl, combine the cream cheese, Parmesan cheese, Panko bread crumbs portion for the filling, green onions, garlic powder, and chopped parsley. Season to taste with salt and pepper. Mix well.
4 oz cream cheese, ¼ cup Parmesan cheese, 3 tablespoon Panko bread crumbs, 2 green onions, ½ teaspoon garlic powder, ¼ cup parsley, salt, pepper
Brush mushrooms with olive oil and remove the stems. Place the mushroom caps on the prepared baking sheet.
12 medium mushrooms, 1 tablespoon olive oil
Fill each mushroom cap with the cream cheese filling mixture, heaping up slightly.
Sprinkle remaining Panko bread crumbs, then Mozzarella cheese on top of each mushroom. Bake 25 minutes in the preheated oven.
2 tablespoon Panko bread crumbs, ½ cup Mozzarella
Remove from oven and let rest for 10 to 15 minutes before serving on a platter. Enjoy!