Preheat oven to 375.
Grease a large baking sheet.
Remove and chop mushroom stems, reserving caps.
Heat a medium skillet over medium-high heat.
Add sausage.
Cook until browned and crumbly, about 5 minutes.
Drain.
Stir in chopped mushroom stems, bread crumbs and 1/4 cup mozzarella into skillet.
Remove skillet from heat.
Spoon sausage mixture into mushroom caps.
Arrange on baking sheet.
Top mushrooms with remaining mozzarella.
Bake until stuffing is hot, about 15 minutes.
Garnish with parsley.