Preheat oven to 375°F (190°C). Clean mushrooms with a damp cloth and remove stems carefully.

In a skillet over medium heat, heat olive oil. Sauté chopped mushroom stems and garlic for about 3 minutes until fragrant.

Add crumbled sausage to the skillet; cook until browned, breaking it into small pieces.

Remove from heat; mix in Gorgonzola, breadcrumbs, parsley, salt, and pepper until well combined.

Generously stuff each mushroom cap with the filling and place on a parchment-lined baking sheet. Top with grated Parmesan.

Bake for 20 minutes or until golden brown.