Preheat oven to 375. Pat chicken dry and place
in a greased 9x13 pan. Add sliced cheese on top
of chicken breasts. In a bowl mix mayonnaise,
sour cream, 1/2 cup Parmesan cheese, salt,
pepper and garlic powder. Spread this over
chicken and sprinkle with remaining Parmesan
cheese. Cover with foil and bake for 40 minutes. Take foil off and bake additional 20 minutes.