Food & Cooking Recipes How to Make Crème Fraîche 3.7 (11) Making this 2-ingredient alternative to sour cream and whipped cream is simple. Jump to recipe Crème fraîche sounds fancy, but you only need two ingredients to make it—heavy cream and buttermilk—and mixing takes moments. It’s also much less expensive than buying in a store. While the method may be simple, you do need to plan ahead, as crème fraîche needs time to develop so the cultures in the buttermilk can thicken and acidify the cream. After you shake the ingredients, the jar must sit out at warm room temperature for eight hours or overnight. Then you move it to the refrigerator for at least 24 hours, though four to five days is optimal to create a thick and creamy substitute for sour cream, or a sophisticated alternative to whipped cream. Credit: Image Professionals GmbH / Getty Images What Is Crème Fraîche and How to Use It Use the best quality, freshest cream you can find. Look for pasteurized, not ultra-pasteurized heavy whipping cream. Directions Combine ingredients: Pour cream and buttermilk into a 2 1/2-cup jar with a lid. Replace the lid, shake well, Let sit on counter: Allow mixture to rest at warm room temperature overnight. Refrigerate: Transfer jar to refrigerator; refrigerate for at least 24 hours before using—the mixture will reach optimal thickness after 4 or 5 days.