1. In a shallow bowl, combine Parmesan, bread crumbs and garlic powder.
2. Slice mushrooms. In a separate shallow bowl, lightly beat egg with a fork (until the yolk and white are combined).
3. Preheat oven to 375 degrees F (190 degrees C).
4. Line baking dish with foil (optional). Spread mushrooms in the bottom of the dish. Top with minced garlic, sliced butter and lemon juice.
5. Season chicken with salt and pepper on all sides. Dip each chicken breast in egg, then into the prepared bread crumb mixture. Place on top of the mushrooms.
6. Bake in the preheated oven for 50 minutes, or until cooked through and golden brown.