Thick, silky, tangy and ever so slightly nutty, crème fraîche is a milder, more elegant French spin on sour cream. It can be difficult — and expensive — to find in stores, but it couldn't be simpler to make your own.
What You WIll Need:
1 cup heavy cream, not ultrapasteurized
1 Tbs. buttermilk
What To Do:
Combine the cream and buttermilk in your small saucepan and gently heat to lukewarm. Do not not allow the mixture to simmer or bubble.
Quickly remove the saucepan from the heat, loosely cover, and let stand at room temperature until thickened, at least overnight but up to 48 hours is okay as well. For crème fraîche to happen you have to let the buttermilk cultures work their thickening magic and that can only happen at room temperature. It’s totally safe to leave at room temperature: The bacteria in the milk converts the sugars —lactose— into lactic acid. This lactic acid lowers the pH of the cream/buttermilk combo which prevents the formation of any illness-causing germy things.
The longer the mixture sits, the thicker and tangier it will become. For best flavor and texture, do chill it for a few hours before using. It will keep for up to two weeks.