Pour some heavy whipping cream into a small jar with lid. Fill about halfway full. Let the cream come to room temperature. Begin shaking your cream in the jar by hand. Fun to let each child have a turn doing this. After a few minutes you will notice the cream thicken.It has become whipped cream.
Continue to shake the cream to make the butter. Soon you will hear liquid sloshing inside the jar again. The cream is separating. Keep shaking! Soon you will sloshing and feel something banging on the sides of the jar as you are shaking. You now have buttermilk and a ball of butter in your jar.
Pour out the buttermilk. You may sprinkle the butter with salt, if desired, and spread it on bread or crackers to eat.