This is a predicament I used to find myself in often until I learned you can freeze leftover buttermilk! Transfer it to an airtight container then pop it in the freezer for up to three months. Or, you try out some of these other delicious recipes made with buttermilk: Oat Flour Buttermilk Pancakes, Buffalo Chicken Salad with Buttermilk Blue Cheese Dressing, or Tomato Salad with Buttermilk Basil Dressing.