Crème fraîche is a soured cream containing about 28% butterfat and with a pH of around 4.5. It is soured with bacterial culture, but is less sour than American sour cream. Crème fraiche is particularly useful in finishing sauces in French cooking because it does not curdle. It is a substitute for sour cream, and is often used as a substitute for butter on toast and whipped cream on desserts.

2 cups heavy cream
2 tablspoons buttermilk

Let stand at room temperature over night until thickened. Then cool in the refrigerator.