In a small saute pan, with a cover, saute mushrooms in 1 tablespoon butter until they begin to brown, remove from pan and season, set aside. In the same pan melt remaining butter and add egg, when the white is slightly firm break the yolk and spread it over the egg. Top the egg with mushrooms and shredded mozzarella and cover the pan. Cook until cheese melts. Garnish with chopped parsley. Remove with a spatula to buttered pumpernickel.