What you need:
6 Cups Heavy Cream
What you do:
Pour six cups of heavy cream into the bowl of a stand mixer with the whisk attached. Cover the opening of the bowl tightly with plastic wrap to prevent liquid from splashing out near the end of the process. Turn the mixer to a medium-high setting and wait between eight and 15 minutes, while the cream passes from whipped cream to over-whipped cream to scrambled-egg fluff to butter and copious amounts of buttermilk. Set aside the buttermilk. On a cutting board, knead the butter, soaking up the resulting liquid with a towel, until no liquid seeps out. Store in the refrigerator.
Makes about 2 cups butter and about 3 cups of buttermilk