3 1/2 cups (or a bit more) whole milk (NOT ultra-pasteurized)
1/4 cup powdered milk (optional)
1/4 cup plain yogurt
fruit or honey
1. Heat the milk on medium-low heat, to 180 degrees. If you want to use the powdered milk for a thicker yogurt, stir it in during heating. Stir occasionally with a wire whisk to prevent burning. (I use quart canning jars to store the yogurt, and if you heat four cups, it will be too much to fit into the jar). DO NOT use ultra-pasteurized milk; it's been heated to too high a temperature and there's virtually nothing left in it to react with the yogurt culture.
2. Let the milk cool to 108-112 degrees. I place my pot of milk in a pan of cold water to speed the process. It doesn't take too long.
3. Mix in 1/4 cup of PLAIN yogurt that has active, live cultures. I buy a small container of yogurt to start, and you don't need fresh yogurt every time. Once you make a quart of yogurt, you can use some of that for your next batch, and so on down the line. You should be able to get about seven generations of yogurt before you need to buy some fresh starter again. I did find powdered yogurt culture called Yogourmet in a health food store, and that works well, too. Just follow the directions on the package; they're similar to those given here.
4. Pour into a yogurt maker and let it sit for 10-12 hours.