Press extra mix-ins into the top of the cookie dough balls before baking so you can see the mix-ins. Use a round cutter to scoot the cookies into perfect circles as soon as they're out of the oven. Just place it around the cookie and sort of shimmy it within the cutter - don't actually cut the edges off. You can also press extra mix-ins into the top of the cookies right out of the oven if there are lots of bare spots.