In French, crème fraîche (krehm FRESH) translates to "fresh cream." But fresh from a cow it is not. Rather, it's cream that's been allowed to ferment. With a decadent, velvety texture, crème fraîche is more delicate than American sour cream. Thickness ranges from pourable to solid. Traditionally, unpasteurized cream is left to ferment on its own, but in the States, it's generally a cultured product. Hispanics make a version known as crema.
Crème fraîche is an extravagant luxury in the dairy aisle, but it's easy to make your own. Blend one tablespoon of cultured buttermilk or sour cream into one cup of heavy cream (avoid ultra-pasteurized) then cover and let sit at room temperature for 12 to 24 hours. When the mixture thickens nicely, use it, or pop it in the fridge. It keeps for a couple of weeks. Alternatively, you can simulate crème fraîche by blending equal parts cream and sour cream. (It's OK. Julia Child did it in a pinch.)
Crème fraîche has several advantages over sour cream. Most notably, it won't curdle when cooked, because its high fat content keeps the proteins from coagulating. You can also whip it, for a tangy take on Chantilly cream. Crème fraîche's crowning achievement may be what it does for fresh berries, but you'll find lots of other uses. Blend it with herbs and lemon juice and dollop onto fish. Substitute it for cream in pan sauces and soups. Or use the money you saved by making your own, and splurge on caviar to take it over the top.
—By Jo Marshall, Writer and Creator of Cookcabulary