Trim the very bottoms of the mushroom stems and discard. Remove the stems from the caps and dice the stems into small pieces.
Preheat oven to 350 degrees F. Spray a mini muffin tin with oil. You can bake these on a cookie sheet, but the mini muffin tin keeps the mushrooms moist and from rolling. Add the mushroom caps, cavity side up, to the mini muffin tins.
In a heavy bottom pan over medium high heat, melt butter. Add diced mushroom stems and allow to cook, undisturbed, until the bottoms start to turn golden brown, about 5 minutes. Add minced garlic, stir, and continue to cook until garlic is fragrant, about 2 minutes. Remove from heat.
In a small bowl, combine Boursin cheese, shredded sharp cheddar, cayenne pepper, half of the parsley, and the cooked mushroom stems with garlic. Mix thoroughly. Add to plastic bag, snip off the corner, and squeeze stuffing mixture into each mushroom until it has all been used.
In a small bowl, combine remaining parsley, bread crumbs, and parmesan. Roll stuffed mushroom in mixture so that the bread crumb mixture sticks to the soft cheese mixture. Return mushrooms to mini muffin tin.
Bake in preheated oven for 20 minutes or until the tops are just starting to turn golden brown. If filling spills out during cooking process, just use a spoon to push it back on when you remove them from the oven. Serve warm.