Crème fraîche is a type of thick cream made from heavy cream with buttermilk, sour cream, or yogurt. If you're ambitious, you can make your own. If not, you can easily substitute it with plain sour cream. The result will be slightly sourer than crème fraîche. Crème fraîche is the more premium of the two (hence its higher price), and it has a more velvety, indulgent texture, thanks to a butterfat content of up to 45%. The sour cream typically contains 20% fat and a richer flavor.