Preheat oven to 350 degrees F (175 degrees C). Grease a baking sheet.
Clean mushrooms with a damp paper towel. Carefully break off stems.
In a medium bowl, mix together the bread crumbs, Parmesan cheese, garlic powder, salt and pepper.
Stuff each mushroom cap with about 1 tablespoon of the bread crumb mixture. Place on the prepared baking sheet.
Drizzle melted butter over stuffed mushrooms.
Bake in preheated oven for 20 minutes. Meanwhile, in a medium bowl, mix together the cream cheese and remaining bread crumb mixture until well blended.
Remove mushrooms from oven. Top each mushroom with about 1 tablespoon of the cream cheese mixture. Return to oven and bake for an additional 10 minutes.