Butter both sides of each piece of bread. Using a heart-shaped cookie cutter, cut the centers out of the pieces of bread. Coat a skillet with the nonstick cooking spray. On low heat, place bread into skillet. Crack egg and pour one egg (keeping the yolk intact) into the center of each piece of bread. Increase heat slightly to med-low and wait for egg whites and egg yolk to cook. Once the whites are firm enough, use a spatula to gently flip the bread and egg and allow to finish cooking. Once done, both sides of the bread should be toasted and the egg gently fried.