All you need is arm strength and heavy cream
I have always wanted to be good in a pinch. I’m a lazy cook and an inconsistent grocery shopper, failures that have given me an outsize appreciation for the ability to make due. My dream chef self is a kitchen-sink gourmand: he can throw together an inspired pasta sauce with a half-dozen tired vegetables, and knows how much molasses to add to white sugar to substitute for light or dark brown sugar—and just happens to have molasses on hand.
It was in this spirit of aspirational preparedness that I first set out to churn my own butter. It’s a project that sounds as impressive as baking bread from scratch, or being the sort of person with homemade chicken stock in the refrigerator at all times, but it’s actually only about as difficult as making your own popsicles. (Still, don’t shy away from bragging about it, at least until people catch on.)
Because it produces soft, room-temperature butter, churning your own butter is a great method for easily throwing together a seasoned butter, like scallion-chive butter for bagels, or garlic butter for garlic bread. Even without any added salt or other seasonings, home-churned butter is light and creamy-tasting, closer to half-and-half than margarine.
Churning butter takes about ten minutes, and requires only a strong arm and a jar with a tightly fitting lid. My jar of choice is an eight-ounce jelly jar, with a second, identical jar for saving the buttermilk. You could, of course, break out the food processor and churn it that way—it would save you time—but this way you don't have to clean anything up afterwards. Just: voila, butter!
Here's how you do it: Fill up your jar of choice a little less than halfway with heavy or whipping cream and seal the lid tightly. Shake. It will take a few minutes, so you may need to switch arms, or enlist a roommate to take a shift. After a while, it will seem like nothing is moving inside the jar—you now have whipped cream. Keep shaking! (Or pause and give it a taste!)
Rather suddenly, the contents will separate into liquid—buttermilk—and a yellow lump that will seem to appear out of nowhere—butter. Unscrew the lid of your jar and pour off the buttermilk into the second jar. Replace the lid and keep shaking, separating the buttermilk from the butter as much as possible. (The seal won’t be as clean and tight as it initially was, so it’s a good idea to shake over the sink.) Repeat.
If you’re using a jelly jar with a two-part lid, shake the jar so your butter lump lands against the lid, turn the jar upright and unscrew. You should be able to lift the flat lid piece off without the butter coming unstuck, leaving any excess buttermilk at the bottom of the jar.
This is the messiest step. Under cool running water, press the butter between your fingers, squeezing out any remaining milk. Form into a ball and place in a container of your choosing—butter tray, ramekin, butter pot. Salt and/or season as desired. Salting the butter will mean it keeps longer, but be careful not to oversalt. Spread all over. Yum.