Be honest: How many times have you made a fairly specific recipe, finished it and then realized you had a ton of leftover ingredients and no idea how to use them outside of making another of the thing you just made? We've all been there. And nothing is more frustrating than throwing away leftovers. With this series, we aim to change that by helping you save money, eliminate waste and try something new all at the same time. This week: buttermilk.