Crème Fraîche is expensive at the grocery store, if you can even find it, but it's easy to make from scratch and has so many uses. To make this classic French condiment, just combine buttermilk and heavy cream and let it sit for 48 hours.
In a sterilized glass jar, stir together heavy cream and buttermilk. Cover with a coffee filter secured by a rubber band and let sit at room temperature (about 70 to 75 degrees) until thickened, about 24 hours.
Transfer to the refrigerator and chill for 24 hours longer. The crème fraîche will continue to thicken. Store covered in the refrigerator for up to 2 weeks.
Notes
Buttermilk: Do not make homemade buttermilk here; you need the active cultures from store-bought buttermilk to make créme fraîche. Look for "cultured buttermilk" on the label.
Yield: One batch makes 2 c. of créme fraîche
Storage: Store covered in the refrigerator for up to 2 weeks.