3 cups milk, you can use prepared powdered milk or store bought milk, whole or 2%
1/2 cup cultured buttermilk (store bought)
In a quart jar, combine milk and buttermilk and mix well. Cover with a coffee filter and let sit out on the counter over night at room temp. In the morning you will have buttermilk! I know this sounds nuts to buy cultured buttermilk to make more, but if you use buttermilk a lot you can just wait till you are near the end of your store bought jug and make your own. We use the powdered milk to make ours. We start with warm water to mix up the powdered milk, then add the cultured buttermilk.