Whenever I am using a recipe that calls for buttermilk, I no longer look in my refrigerator to see if that lonely carton of buttermilk I bought last fall is still any good. When does buttermilk go sour anyway?
Neither do I dig through my pantry to see if I have any of that powdered buttermilk you can buy in the baking aisle.
I simply add 1 tablespoon of vinegar or lemon juice to a cup of milk and let it sit for 5 minutes. Wah-lah! Buttermilk!