Why make your own butter? For one thing, fresh butter tastes better. That should be reason enough. Butter is also one of those awesomely unique food items that, when making it yourself, yields more ingredients than you started with, butter and buttermilk. From that point, there are tons of possibilities of what to use each for. The form of buttermilk produced when making butter is old-fashioned buttermilk in its truest form. It's the real deal and not buttermilk how it is produced today (milk fermented by bacteria cultures), and therefore it is thinner, less tangy, and slightly sweeter than commercial buttermilk. With that being said, it is best NOT to use this old-fashioned buttermilk in baking recipes that call for it, as such recipes typically include alkaline baking soda to balance the acidity of commercial buttermilk. Instead use this buttermilk in non-leavened recipes such as in dairy brines, salad dressings, and smoothies.
When using a standing or handheld electric mixer, churning your own sweet cream butter and buttermilk is ridiculously simple, cost efficient, and fun for do-it-yourself aficionados. You can also pour the sweet cream into a mason jar and hand-shake it like crazy for 10-12 minutes (giving yourself a good arm workout), but I recommend sticking with the electric mixer method. Give it a try, y'all. Channel your inner dairy-farmer. It's completely worth it.
Let cream sit out at room temperature for 1 hour. Using an electric mixer, whip cream on low setting for 2-3 minutes. Increase speed to high and continue whipping for about 15-18 minutes, or until the butter solids separate from the buttermilk. (Stopping the process after 10-12 minutes should give you whipped butter, if desired.) Spoon butter solids into a small mesh strainer and push/squeeze out buttermilk into a bowl, trying to get out as much buttermilk as possible. (Most methods for preparing butter recommend kneading the butter in an ice-cold water bath to remove all buttermilk from the butter solids, but I find this unnecessary as long as you get all the buttermilk out when straining it thoroughly in a strainer. Having buttermilk remain in the butter when not properly strained will cause the butter to turn sour.) Gently squeeze the butter with your hands to remove any remaining buttermilk (don't overdo it, as butter melts at body temperature). Season with salt and/or herbs if desired. The butter should last, refrigerated, for 4-6 weeks (if not longer). You can freeze it, as well, to allow for longer storage.