My blog stats are showing a lot of people ending up here after searching for “how to make buttermilk from regular milk”. You can’t. Buttermilk — real buttermilk — is made from cream, not milk. You can only make a substitute for buttermilk from regular milk. However, there’s no law preventing cultured skim milk from being sold as “buttermilk”, and that’s usually what you find in the supermarket — not real buttermilk at all, which is the liquid left over after churning cultured cream to make butter. Since most of the butter made in this country is made from sweet cream, not cultured cream, there isn’t a huge supply of proper buttermilk. A few days ago, I described how it’s done, and you too can do it at home if you like. It will probably cost more than what you can buy at the supermarket. (Note that yogurt culture is not the same thing as the culture used to make crème fraîche and cultured butter!)