1. Lightly saute mushrooms in butter, sherry and garlic on medium heat. Drain on paper towel.
2. Cut up brie into 12 pieces (I like the rind but it can also be removed) and place in mushrooms. Add a 1/2 tsp of the pesto on top of each.
3. Place under the broiler until cheese melts (usually less than 1 minute). Serve immediately.