-small container of plain yogurt
-gallon of milk
-dutch oven with a lid
-your favorite spoon for stirring
Preheat your oven to the lowest temperature. Turn it off as soon as it reaches that temp.
1. Dump gallon of milk into your dutch oven. Heat to 180 degrees over medium heat. Stir often so the milk doesn't scorch.
2. Cool to 110 degrees. I like to partially fill my sink with cold water or ice water (or frozen ice packs) and then put my pot in the sink to cool. Keep stirring to release the heat.
3. Add 4 tablespoons of plain yogurt. Stir. Cover.
4. Place covered pot in the oven. Cover the lid with a folded bath towel and try to wrap the towel around the sides of the pot. I fold the towel in thirds the long way.
5. Turn on your oven light and forget about the yogurt for 6 hours. The longer you let the yogurt sit, the tangier it will get. I like the taste at 6 hours.
Now you have a couple of options. You can eat your yogurt (and/or add things like honey, brown sugar, strawberry puree, applesauce and cinnamon, blueberries, vanilla, etc) OR you can strain your yogurt. I prefer a Greek style of yogurt so I always strain mine before eating it.
Gather a tea towel or cheese cloth and lay in a colander (a steamer basket works well too). Scoop yogurt into cloth and cover. Let drain in fridge overnight or until it has reached your desired thickness. Make sure you have a pot or pan under the colander or you will have a mess.