All you need to make butter is a bowl, a whisk, and some cream.
The cream should have no additives, just cream, and if it’s créme fraiche for making cultured butter, then it will have cultures as well (here’s my recipe for culturing cream at home).
Put the cream in the bowl and whisk. After a fair amount of whisking it will become whipped cream. Continue whisking and whisking and the whipped cream will become more yellow. Soon after this you’ll begin to see some liquid forming. Continue whisking, more of the buttermilk will separate from the butter.
You don’t have to do all the whisking at once, you can come back to it every now and then. Or you can use a stand mixer or hand mixer.
Once it looks as though all the buttermilk that’s going to come out has been released, strain the butter over a mixing bowl, reserving the buttermilk for recipes.
Put the butter in a bowl of very cold water. Knead with your hands a few times to release even more of the remaining milk.
Drain the water and replace with more very cold water. Knead again.
Remove the butter from the water, kneading as much water out of it as you can. Shape it and store it in beeswax wraps or glass jars. Enjoy!