Crinkle cookies usually crack because the sugar coating is too thin, the ingredients aren't fresh enough, or the oven isn't hot enough. You can roll the cookie dough balls into Granulated Sugar and then Powdered Sugar if you like, to ensure you get that perfect cracked look, but I've not had an issue with using just Powdered Sugar for this recipe. Make sure to use a box mix that is in-date. Always preheat the oven before baking cookies. Baking cookies in a hot oven for less time will also keep their centers chewy.