- 2/3 cup cold heavy whipping cream
- 1 1-cup canning jar with lid and ring
- Pour cream into the jar and screw on the lid. Shake jar until butter forms a soft lump, 15 to 20 minutes. Continue to shake until buttermilk separates out of the lump and the jar contains a solid lump of butter and liquid buttermilk.
- Pour contents of the jar into a fine mesh strainer and strain out the buttermilk, leaving the solid butter. Remove the lump of butter and wrap in plastic wrap. Refrigerate until needed.