- 2 cups heavy cream
- 3 tablespoons cultured buttermilk
- Combine cream and buttermilk in a glass jar. Cover tightly with cheesecloth (or any breathable material) and let sit at room temperature (70 to 75 degrees F (21 to 24 degrees C)) for 24 hours. Stir, screw on lid, and refrigerate for 24 hours before using.