Butter
Heavy whipping cream, room temperature
Salt, optional
Fill a jar about halfway full of cream (I used 1 cup), then add a marble. Cover tightly with a lid. Shake the jar for about 10 minutes, or until the butter separates from the liquid. Remove the butter from the jar and squeeze the excess liquid out of the butter; rinse with cold water. Add salt to taste, if desired, and knead into the butter. Cover and refrigerate.
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