The first time I mixed buttermilk and heavy cream and let it sit overnight until it became thick and creamy, my mind was honestly more blown than it had been since. SCD-Cream-Yogurt_-2.jpg' alt='Creme Fraiche' title='Creme Fraiche' />Creme Fraiche Recipe Food Network. Mix 3 parts fresh heavy cream to 1 part fresh buttermilk in a clean jar or crock. Cover with cloth. Store in a warm area for 2. Stir. Mixture should be thick and creamy.