If you want to make a double crust, can you double the recipe or do you need to mix each separately?

Hi Susan! You can double the quantities and proceed with the method as written—though the mixing at each step might take a little longer. Just pay attention to the visual cues and you should be all good. There are reference photos in the article, in case that's helpful: https://food52.com/blog/23677-all-butter-flaky-pie-crust-recipe-without-shortening-stand-mixer