Pour 1 cup of heavy cream or whipping cream into a clean jar or bowl
Add 1 to 2 tablespoons of cultured buttermilk or plain yogurt
Stir gently until combined
Cover loosely with a lid or cloth
Let it sit at room temperature for 12 to 24 hours
Check for a thickened, tangy texture
Refrigerate for at least 4 hours before using
Stir before serving
Store in the refrigerator and use within 1 to 2 weeks