Preheat the Oven: Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper or aluminum foil.
Prepare the Mushrooms: Clean the mushrooms by wiping them with a damp paper towel to remove any dirt. Carefully remove the stems from the mushrooms and roughly chop them. Place the mushroom caps on the prepared baking sheet, cavity-side up.
Cook stems: Heat butter in a medium skillet over medium heat. Add mushroom stems and cook for 4-5 minutes until softened. Add garlic and cook for about 30 seconds then add breadcrumbs. Cook for 2-3 minutes or until golden brown. Remove from heat.
Prepare the Filling: In a mixing bowl, combine the breadcrumbs, grated Parmesan cheese, minced garlic, chopped fresh parsley, olive oil, salt, and pepper. Mix well until all the ingredients are evenly incorporated.
Stuff the Mushrooms: Using a spoon or your hands, fill each mushroom cap generously with the breadcrumb mixture, pressing down gently to pack it in and create a mound on top.
Bake the Stuffed Mushrooms: Place the baking sheet with the stuffed mushrooms in the preheated oven. Bake for 15-20 minutes or until the mushrooms are tender and the filling is golden brown and crispy on top.
Serve: Once the stuffed mushrooms are cooked, remove them from the oven and let them cool slightly before serving. Garnish with additional chopped parsley or grated Parmesan cheese if desired.
Enjoy: Serve the stuffed mushrooms warm as an appetizer, side dish, or party snack. Enjoy the delicious combination of savory flavors and tender mushrooms with friends and family!