Use creamy peanut butter for the smoothest texture; natural peanut butter can be used if well-stirred but may make the mixture softer—add a little extra confectioners' sugar if needed. Swap semisweet chocolate with milk or dark chocolate to taste. For tidy dipping, keep the peanut butter balls well chilled. Buckeyes keep 1 week refrigerated or up to 2 months frozen; separate layers with parchment.