Melt butter/margarine in a small pot, along with the garlic. Set aside to cool enough to be touchable by the hand (as you will be in contact with the butter in a short while)
In a shallow bowl mix the bread crumbs, cheddar & parmesan cheeses, pepper, and salt.
Take a chicken breast and dip it into the garlic butter, followed by coating it with the bread crumb mixture. Place into a pan (lined with parchment paper, or sprayed), and repeat for every other chicken breast. If there is any remaining garlic butter or bread crumb mixture, pour or pat it onto the chicken breasts.
Place the chicken into the pre-heated oven, and cook for 25-30 minutes, or until the chicken is cooked through and the edges begin to crisp