1. Preheat oven to 325 degrees. Cut top of garlic head off. Place garlic on piece of aluminum foil. Drizzle with olive oil and sprinkle with sea salt. Wrap foil tightly around garlic and place into oven. Bake for 30-40 minutes or until softened. Squeeze roasted cloves out of head of garlic.
2. In a medium bowl, combine roasted garlic cloves, mayonnaise, white cheddar, Parmesan and parsley. Stir to mix well. Season with salt and pepper.
3. Carefully remove stems from mushroom caps. Spoon cheese mixture into each cap. Place on baking sheet.
4. Increase oven heat to 375 degrees. Bake mushrooms for 15-20 minutes or until cheese is melted and bubbly.
These can be stuffed in advance and refrigerated until ready to bake.