No, I do not have a cow. But I have a friend who does. I get my raw milk from her. I skim off the cream, and freeze it until I have a quart. Some cows have more milk than others. Cream is a by-product of genetics. There are certain breeds that are known for higher cream percentage. The Jersey is one of those breeds, however it still goes by genetics. Not all jerseys give lots of cream.
Anyway, after I have saved up at least a quart of cream, I make butter.
There are times when I want something a little special. So I make cultured butter. Steve had found a brand new yogurt maker at a yard sale for two dollars. I have used it several times. The first time that I used it, I bought a package of yogurt starter. The yogurt was as firm as the Greek yogurt in the store. The second time I used it, I used the last of the yogurt as a starter. The result was a little thinner. The third time that I used it, I used the last of batch #2 to start it. The result was even thinner. The taste was the same in each batch though. My point is, You do not need a new packet of culture for each batch. But I will use a new packet for every 4th batch.
I just made batch number 4. It was nice and firm. I added about 1/2 cup of that new batch to my jar of cream, and let it set out on the counter for 24 hours to allow the yogurt to culture the cream. The good bacteria in the yogurt grows by feeding off of the cream. Now I have cream full of friendly bacteria. Then I put it in the fridge overnight to halt the culturing process. Today, I took the jar out of the fridge, and brought it back to room temp.
Then into my Kitchen Aid mixer to make butter.
When I was finished I had 4 oz (by weight) of cultured butter and 3 cups of a mild tasting buttermilk.