Next time you find yourself with leftover buttermilk after whipping up your favorite coffee cake or a batch of biscuits, here's a tip: freeze it!We freeze leftover buttermilk in 1 Tablespoon portions in ice cube trays. Once frozen, the cubes can be stored in a freezer bag, and since they're already measured, we can just pull out the number of tablespoon-cubes we need for our recipe.
You can thaw the cubes overnight in the refrigerator or melt them at a low power in the microwave.
Freezing will cause the solids and the whey in the buttermilk to separate. Before using in your recipe, whisk the buttermilk or run it in a blender until the solids and the whey reincorporate.