Preheat oven to 400°.
Lightly spoon flours into dry measuring cups; level with a knife. Combine flours, baking powder, and salt in a bowl; make a well in center of mixture. Combine brown sugar, honey, and peanut butter in a bowl; stir well with a whisk. Add milk, egg whites, and egg to honey mixture; stir well. Add honey mixture to flour mixture; stir just until moist. Spoon batter into 16 muffin cups coated with cooking spray. Sprinkle granulated sugar evenly over tops. Bake at 400° for 18 minutes or until muffins spring back when touched lightly in center. Remove muffins from pans immediately; place on a wire rack.