Prepare the Mushrooms

1. Preheat the Oven: Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper for easy cleanup.
2. Clean the Mushrooms: Gently wipe the mushrooms with a damp paper towel to remove any dirt. Remove the stems from the mushrooms, carefully scooping out the insides with a spoon. Set the mushroom caps aside and chop the stems finely for the filling.
3. Prepare the Filling: Heat olive oil in a skillet over medium heat. Add the chopped mushroom stems and garlic, cooking for 3-4 minutes until softened. Remove from heat and let cool slightly.
4. Mix the Filling: In a bowl, combine the cooled mushroom stems and garlic mixture with Boursin cheese, Parmesan cheese, fresh parsley, salt, and pepper. Stir until well combined.

Stuff the Mushrooms

1. Stuff the Mushroom Caps: Spoon the cheese mixture into the mushroom caps, packing the filling in tightly.
2. Top with Breadcrumbs (Optional): If using breadcrumbs, sprinkle a small amount over the top of each stuffed mushroom for a crispy, golden finish.

Bake the Mushrooms

1. Bake: Place the stuffed mushrooms on the prepared baking sheet and bake for 18-20 minutes, or until the mushrooms are tender and the filling is golden and bubbly.