Wash hands with soap and water.
Preheat oven to 450 ˚F.
Gently rub mushrooms under cold running water. Remove the stems from mushrooms, chop and set aside.
In a skillet cook the ground pork sausage, stirring frequently, until internal temperature reaches 160 ˚F on food thermometer (about 8-10minutes).
Wash hands with soap and water after handling uncooked sausage.
Remove sausage from the skillet and drain leftover drippings into a bowl.
In a skillet add 2 tablespoons of leftover drippings. Cook mushroom stems on medium heat for 5 to 10 minutes, until tender and browned.
Remove from heat and stir in sausage, breadcrumbs, and mozzarella cheese.
Fill mushroom caps with the sausage mixture and place on a baking sheet.
Bake until the internal temperature reaches 160°F on a food thermometer.
If desired, top the stuffed mushrooms with more mozzarella cheese and return to the oven just until the cheese has melted.