In this video, you’ll see how to make homemade crème fraiche by simply combining heavy whipping cream and cultured buttermilk in a perfectly sterilize... See mored jar. This is so incredibly easy! You’ll see how to cover the mixture in a way that allows it to still breathe. Then you’ll see how to grow the culture by first setting the mixture aside in a warm place for 24 hours, and then allowing the mix to thicken and become tangier in the refrigerator for an additional 24 hours. The crème fraiche comes out of the fridge thick and creamy with a deep nutty flavor that goes so far beyond store-bought sour cream. You can cook with this like cream, and it won’t separate or curdle. Get the ingredients for Chef John’s Creme Fraiche.