Every morning an Amish housewife skims cream from milk. Every 2-3 days — the churn.
Process
Room temperature cream (cold won't churn). Into the churn (wooden barrel with dasher). Beat rhythmically 15-20 minutes. First — whipped cream. Then — butter flakes and liquid (buttermilk). Collect flakes, wash with cold water (remove buttermilk — or it'll go rancid). Squeeze. Salt.
Without a Churn
Jar with lid. Half-fill with cream. Shake 20-30 minutes. Same result, but arms will tire.
Buttermilk
Don't discard. Pancakes with buttermilk — fluffier. Meat marinade — tenderizes. Bread dough — tanginess.
Storage
Unsalted: 1-2 weeks in cellar. Salted: 3-4 weeks. Clarified (ghee): 3-6 months at room temp — better than butter for frying.