So, ever since I found
an entry on making butter on the Cooking for Engineers site a few months ago, I've been wanting to try it.
Yesterday, I did.
Cream after I'd let it sit out overnight and then shook it until it sounded solid (I only used a pint of cream: it seemed reasonable to do this in a small batch)
Butter and buttermilk in a water glass (I'm not crazy: nothing else was tall enough to prevent splattering but still small enough to get the stuff to touch the beaters) just before I poured off the buttermilk
Butter, after kneading in icewater
The finished product... needs salt, mostly. But maybe leaving the cream out longer to sour more would also have helped. Dunno. We'll see with the next batch.