Actually, making cultured butter is quite easy, albeit a bit messy, but no more so than regular butter and the flavor return is tremendous.
To begin, take two quarts of the best heavy cream you can find, but not ultra-pasturized. Luckily I have a few very good local dairies and chose to use Sheeder Cloverleaf Dairy because my favorite local grocery store carries it. By the way, their skim milk is divine, its like NOT drinking skim milk its so good!
After chilling for a bit, rinse and knead, then rinse and knead some more. Your goal is to have your final rinse water very clear without a trace of cloudiness. All the buttermilk needs to be rinsed out so your butter won't sour and taste bad. I just kneaded it with my hands, and now my hands are literally buttery soft.
After kneading and rinsing very very well, you will now press out the water. Using a rubber spatula, press and smooth the butter against the sides of the bowl and pour out any water that "weeps" out the butter. Keep pressing and draining until no more water remains. At this point, your butter is finished, or you can salt it using pickling salt or sea salt. I chose to salt it. Salting also may help the butter firm up a bit.
I do hope you will give this a try, I used 2 quarts of cream and made alot, and I'm sure it will keep well in the freezer.