While you can buy creme fraiche in the dairy case these days, it’s easy and much cheaper to make. It not only adds great flavor, but keeps much longer than plain old cream. Add a spoonfull to soups, sauces, or anything that needs a just a bit of creamy flavor, or drizzle a little over grilled vegetables, salads, crab cakes, latkes, or damn near anything.
In a nonreactive container (glass or stainless), stir together about 3 parts heavy cream and 1 part plain yogurt or buttermilk. For a half-pint container of cream, that means a couple of good spoonfulls of yogurt. I use Nancy’s yogurt since it’s packed with the live cultures that make this work.
Mix well, cover, and put someplace warm. If you have an old gas stove with standing pilot lights, set the container on it over the pilots. Otherwise, the top of the refrigerator or anyplace where it will stay warm is okay. Let it sit overnight or at least 12 hours. When it looks thick, put it in the refrigerator; it will keep for at least a week or two.