Pour the whipping cream into a plastic pint-sized jar with a screw-top lid (a peanut butter or mayo jar both work well).and add a pinch of salt if desired. Screw on the the lid tight-- I usually reinforce with masking tape as a precaution.
Take turn with the children and shake the jar. We usually pick a song to sing for each child's turn. This takes a while-- about 5 minutes or so.
Drain the liquid from the butter. This is the buttermilk, and some of the children may want to try it (I offer **very small tastes** in paper cups). Add more salt, or honey, to taste if desired.
Serve the butter at once on crackers or bread, or chill to serve later.