Pour heavy cream into mixer bowl.
Turn on mixer to "4" setting for 2 minutes, then up to "6" for 3 minutes. At this point, you should have whipped cream!
Continue mixing on "6" for 5 more minutes. The cream will begin to separate. Scrape sides with spatula as necessary.
Mix for another minute or until you hear sloshing.
Drape towel over the mixer to prevent splatters.
Mix for an additional minute. Turn off mixer, remove towel. The butter will be in the whisk and buttermilk will be in the base of the bowl!
Transfer butter to small bowl, then transfer to a paper towel. Roll tightly to squeeze out excess liquid. Repeat as necessary.
Transfer butter and buttermilk to air tight containers and store in the refrigerator.