Step 1Heat the cream and buttermilk in a saucepan to 100 degrees. Remove the mixture from the heat and pour it into a glass container. Cover with plastic wrap and store in a warm spot for 24 hours, until somewhat thickened.
Step 2Put the creme fraiche in the refrigerator overnight. Take it out of the refrigerator and let it sit in a warm spot for another 24 hours. This will further thicken the creme fraiche.
Step 3Put the creme fraiche back in the refrigerator until ready to use. It will keep for up to 10 days refrigerated.