In a large bowl, thoroughly mix together the ground beef with salt, pepper and parsley.
Scoop up about one tablespoon of the meat mixture, roll it into a ball, and place it on top of a mushroom.
Bake at 180° for 20 minutes.
Remove the stuffed meatballs from the oven, sprinkle them with mozzarella cheese, then toss them back in the oven until the cheese melts.
