Butter can be expensive, and if you can get your hands on cream with no other ingredients, you can save a bit by making it yourself. If cost effectiveness is not a priority for you, this is definitely a SHTF skill if you ever find yourself holed up with a cow!
I will confess that I tried to make it straight from the milk but failed, maybe I should try using heavy whipping cream next time instead. You’ll need a kitchen mixer but a food processor would work. Check the video below for the instructions: