How to make sour cream (or creme fraiche) from scratch with only 2 ingredients.
Combine heavy cream and buttermilk in a glass bowl or mason jar and give it a good stir. Cover with a piece of cheesecloth or a clean kitchen towel, and secure it with a rubber band.
Allow to sit in a warm environment, ideally 80-85 degrees, for 24 hours. When it’s ready, it’ll smell slightly tart and will have thickened. While it isn’t as thick as commercial sour cream, it should be thick enough to cling to a spoon and ribbon as you tilt the spoon over.
Once you have your desired thickness, you should store sour cream in the refrigerator. It should last 3-5 days refrigerated.