Put some cream [not ULTRA pasteurized, just pasteurized] in a bowl, make whip cream but don't quit. Keep on whipping, the whipped cream will turn to butter. Watch the ball start to turn and slow the mixer down a bit because when all the cream has churned to butter the whey [water in the milk] will break loose from the blob of butter and sling all over the counter and your wife will say unkind things to you, then pick out the ball of butter and let it set in a colander in cheese cloth for a while. The longer you churn it the more whey will come out and the higher the butter fat level will be. You can add salt to the cream if you want but since I never want, i can't tell you how much.
The time is less than 5 minutes not counting the clean up after your wife gets done explaining her point of view.
I use a 1/2 gallon of Heavy cream and yield about 1 1/2 pounds. Using Costco pricing here, that is about $3 dollars a pound, Not bad.
I'm trying to find a source for un-pasteurized cream to make cultured butter like the Eurpeans still do.
May you eat well,