How to Make Sour Cream
Sour cream is the delicious base for a variety of dips and sauces, and making your own couldn't be easier. All you'll need is a small amount of store-bought cultured buttermilk (1 percent is fine), a pint of heavy cream and a container large enough to hold the cream. To start, pour 1/4 cup of the buttermilk into the bottom of the container.
Pour in the heavy cream, then stir or whisk to combine the cream and buttermilk thoroughly.
Cover the container with a piece of cheesecloth, a butter muslin or a clean kitchen towel, and secure with a rubber band.
Keep the container out in a warm environment for about 24 hours. If the ambient temperature in your kitchen is warm, you may leave the container out on the counter. Or, place it in a cool oven with the light on. Optimally you want it to be about 80 to 85 degrees F.
After 24 hours, your sour cream should have thickened, and it will have a pleasantly tart flavor. It will cling to a spoon and will ribbon. The longer you leave the cream to culture, the thicker and tangier it will get.
Use your homemade sour cream as you would regular store-bought sour cream, like in a delicious herb dip.