Pour heavy whipping cream into a small mason jar or another jar with a tight-fitting lid.
Secure the lid tightly and shake vigorously.
Continue shaking until the cream first becomes whipped cream, then separates into solid butter and liquid buttermilk.
Pour off the liquid.
Remove the butter from the jar and gently press out any remaining liquid.
Serve immediately or refrigerate for about 1 hour for a firmer texture.
For salted butter, mix in a small pinch of salt to taste.
Notes
This recipe makes a small batch of unsalted homemade butter.The liquid that separates from the butter can be discarded or saved for another use.Store the finished butter covered in the refrigerator.