I used 500mls/1 pint of cream and it yielded just under 250gms/half a pound of butter.
Put the cream in a stand mixer and whip
You have to wash the butter to make sure all the buttermilk is out as it would turn the butter rancid. Just knead until the water is clear.
Return it to the mixer bowl and whip in salt if wanted and two tablespoons of oil to make it fridge spreadable. Then just pop it in a container