When a recipe calls for buttermilk, do you really need it? What do you do when you’re caught without it? And how do you use up any leftovers?
Davwud notes that buttermilk freezes well, so it’s easy to portion and store the remainder of a quart for future use. If your main use for buttermilk is in baking, paulj recommends keeping powdered buttermilk on hand (add the appropriate amount of powder with the dry ingredients and water with the wet ingredients).
Cooks can also substitute plain milk with some acid added to replicate buttermilk’s acidity; use 1 tablespoon lemon juice or white wine vinegar per cup of milk. Let it sit a few minutes and it will thicken up like buttermilk. In many recipes, other acidic dairy products, such as yogurt or sour cream, can replace buttermilk, says soupkitten, and Bryn suggests thinning yogurt with plain milk.
Board Link: How to make Buttermilk