Preheat oven to 375 degrees and spay a 9x13 baking dish with vegetable oil spray.
Remove stems from the mushrooms carefully and mince the stems.
In a large skillet add the stems, butter, garlic, salt, and pepper on medium heat.
Cook and stir for 5-6 minutes until softened and browned.
Stir in 1/4 cup panko, cream cheese, and parsley until well mixed.
Spoon the mixture into each of the mushroom caps.
In a small bowl stir together the Parmesan cheese and 1/4 cup of remaining Panko.
Dip the mushroom with filling into the breadcrumb cheese mixture to coat the cheese and mushroom filling.
Bake, uncovered, for 22-25 minutes.