This post was originally posted at our family blog, link in the sidebar.
After awhile, the contents of the jar will become frothy. Keep shaking until you hear it "thudding" around inside, the sides of the jar starts to clear up and you can see the butter inside.Now it is time to separate the butter from the,um, butter milk. I lined a colander with cheese cloth and put it over a pan. Dump the contents of the jar into the lined colander. Let the buttermilk strain through. I caught it in a pan, to save for some homemade biscuits later. Once all the initial buttermilk has drained through, rinse the butter under cold water. Stir with a fork, rinsing out any remaining buttermilk, until water turns clear.