1 pint heavy cream
starter of choice: 1 heirloom buttermilk starter or 2 tbsp cultured buttermilk, yogurt or kefir
Combine heavy cream and starter in a clean 1-quart jar. Cover jar with butter muslin cloth and secure muslin with a rubber band. Let stand at room temperature for 1-3 days or until thickened. Stir daily. Refrigerate once thickened to your desired consistency. The cream will continue to thicken and develop flavor in the refrigerator, where it will keep for about two weeks.