Remove sausage from casing and brown in skillet. Drain and reserve. In food processor or blender container, combine cream cheese, garlic, parsley, lemon juice and pepper; mix until smooth. Place mushroom caps on lightly greased baking sheet; season with salt and pepper, if desired. Fill mushroom cap with sausage, top with cream cheese mixture; sprinkle with Parmesan cheese. Bake at 450 F for 8-10 minutes or until lightly brown.