Who keeps buttermilk lying around in the fridge? I sure don't. And usually, when a recipe calls for buttermilk, I get all flustered and start looking for an alternative recipe that will allow me to avoid the need for this obscure ingredient.
Well, buttermilk is not a big deal. Really. Its consistency is different from regular milk, but there is no need to fret about not having it. There is likely not even any need to bother going out to purchase some, even if you do have the time or energy. Simply make your own -- the consistency will be slightly different, but the taste will be the exact same.
Pour 1 tablespoon of white vinegar or lemon juice into a measuring cup. Then, add enough milk until it becomes 1 cup total of liquid. Stir, and allow to sit for five minutes. Done! Use in a recipe as it calls for buttermilk.