Creme fraiche is a thick, lightly soured cultured cream — heavy cream gently fermented by lactic-acid bacteria into a glossy, spoonable mass of about thirty percent fat or more. Richer and far less sharp than sour cream, with only a faint clean tang behind a deep, nutty, buttery richness, it is a cornerstone of French cooking: stirred into pan sauces and soups, spooned over fruit and galettes, and dolloped on everything from smoked salmon to baked potatoes.