Preheat oven to 350°F. Remove mushroom stems and discard. In a food processor, combine egg white, bread crumbs and cheese. Process about 5 seconds or until mixture is combined.

Evenly spoon cheese mixture into mushroom caps. Arrange on a greased baking sheet. Bake about 15 minutes or until mushrooms are golden and tender. Remove from oven. Top with parsley leaves, if desired. Serve immediately.