1. Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper for easy clean-up.
2. Clean the mushrooms by gently wiping them with a damp paper towel to remove any dirt. Remove the stems and set them aside for another use, if desired.
3. Place the mushroom caps on the prepared baking sheet, gill side up. Drizzle with olive oil and season with a pinch of salt and pepper.

1. In a medium-sized mixing bowl, combine the Gorgonzola cheese, cream cheese, chopped walnuts, parsley, minced garlic, and black pepper. Mix until the ingredients are well-combined and form a cohesive stuffing mixture.
2. Using a small spoon, carefully fill each mushroom cap with the cheese and walnut mixture, pressing it down lightly to ensure it stays in place.

1. Bake the stuffed mushrooms in the preheated oven for 20-25 minutes, or until the mushrooms are tender and the stuffing is golden and bubbling.
2. While the mushrooms are baking, prepare the balsamic drizzle. In a small saucepan over medium heat, combine the balsamic vinegar and honey. Bring to a simmer and cook for about 5 minutes, or until the mixture has reduced by half and becomes slightly syrupy. Remove from heat and let it cool slightly.
3. Once the stuffed mushrooms are done baking, remove them from the oven and allow them to cool for a few minutes.
4. Drizzle the balsamic reduction over the stuffed mushrooms just before serving, and garnish with additional parsley if desired.
5. Serve these delicious Gorgonzola and Walnut Stuffed Mushrooms warm as an elegant Italian appetizer sure to impress your guests!