Pour cream into a blender, food processor, or large, empty jar with a tight fitting lid.
Secure the lid, and turn the processor on at it’s low setting.
It will only take a minute or two before you have whipping cream. If you want salted butter, stop your processor and add it. Just a pinch or two will do the trick, but you should taste it to be sure.
Secure the lid again, and continue to blend on low. In another minute or two, you will start to see a lot of liquid. Once you have this liquid, you’re done!
Take a large cup, or bowl and place some cheese cloth, a paper coffee filter or a small, fine-meshed sieve in it. Pour the butter into the cloth and let it drain.
Now carefully squeeze out some of the remaining buttermilk, gently unwrap the cheese cloth, and transfer the butter to your butter dish.
Important note: You must be sure to remove all the butter milk from the butter. If you don't churn the butter enough, the buttermilk that remains in the butter will sour and spoil your butter. Feel free to blend a second time in the processor or hang the butter to drip off any residual butter milk in the cheese cloth for a couple hours.
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Notes
Please note that the nutrition data below is a ballpark figure. Exact data is not possible.