I make a fair number of things (cakes, meatballs, etc.) that call for a relatively small amount of buttermilk. Maybe 1/2 to 1 cup. So I end up buying a quart and then tossing what I don't use (I don't make these things that often). I know I can kind of simulate buttermilk with regular milk and a little vinegar, but America's Test Kitchen recently did a segment on this where they suggested buttermilk powder (presumably you mix it with water to get buttermilk).
Anyone out there every use this stuff? If so, how good is it? And is it available in any grocery store? It just seems like a much more frugal way to have buttermilk on hand.