We used to make butter when we were kids back in the fifties.
All you need is a jam jar with lid and some cream. Fill the jar about two thirds to three quarters with cream and then slosh it around for about 15-20 minutes.
Tearing around on a bike with the jar bouncing around in the basket on the front used to do the trick without even thinking it was an effort!
A lump of butter forms and you can drink the whey which is a bit like skimmed milk.
Simples!
John