Take 2 cups of heavy cream (preferably not ultra-pasteurized), and place into a clean glass jar. Add 2 tablespoons of buttermilk and seal with a lid. Shake the mixture for 20 seconds, then unscrew the lid, but so it’s still covering the jar. Leave the jar on the counter top undisturbed for 18 – 36 hours, depending on how sour and thick you want the final product to be. The time it takes to make will also change with the temperature of the room. Refrigerate for 2 hours before using, as this will further thicken the crème fraîche. Keep refrigerated and use within two weeks. Try using this in mashed potatoes, over pancakes, in salad dressing, in a soup or lightly whipped and over a dessert.