Whisk 1 cup fresh, raw cream and 3 tablespoons of starter together. For your starter you can use sour cream, yogurt or milk kefir.
I prefer to use sour cream as my starter. You can use a couple of tablespoons of sour cream from your last batch (if you have any left). If not, store bought works great.
Cover and let sit on your kitchen counter for 24 hours. Then transfer to the refrigerator.
The sour cream will continue to sour each day as it hangs out in the refrigerator. The first 2 days it is going to taste like creme fraiche- delicious. About day 3-5 it sours perfectly and will remind you of the sour cream you are accustomed to eating. On day 7 it will taste like a cow. Give it to the chickens.