To make homemade butter without using a churn, shake heavy whipping cream in a jar until it thickens, pour off the buttermilk that forms during shaking, and knead the butter to work out additional buttermilk. Salt the butter if desired, and refrigerate it. The process takes around 10 minutes to complete.
To begin, choose a jar for the butter; a baby food jar or other small jar with a lid is a good choice for making small amounts of butter. Fill the jar around halfway with your choice of heavy whipping cream. Tightly screw the lid on the jar. Shake the jar in an up-and-down motion until the cream thickens and starts to stick together. It takes around 10 minutes of shaking to make homemade butter.
As you shake the jar, buttermilk separates from the cream. Open the jar, pour the buttermilk from the jar, collecting it in another container and leaving the butter in the jar. Remove the butter, and knead it under cold running water for a few minutes. This works out any remnants of buttermilk and helps the butter stay fresher longer.
For salted butter, knead in salt to taste if desired. Refrigerate the butter inside the jar after salting.