Heat up milk but don't bring to boil. I added vanilla beans to infuse my milk (pick out beans once infused)
Let the milk cool down a bit so that it is rather warm.
Add plain yogurt to a mixing bowl with milk and combine with a whisk.
Keep pots ready in a yogurt maker (or tray if you are doing it in the oven) and pour yogurt milk mixture into the pots.
Turn on yogurt maker and cover. Follow the instructions of your yogurt maker. With my yogurt maker, I turn on the device to add heat for 3 hours while it's setting and then I turn it off and the yogurt sets further. For oven turn on light in oven and place tray with pots covered in and let set. Setting time for both techniques varies between 8-12 hours.
When set, store your yogurt in the fridge until further use. You can start the whole process anew by keeping some yogurt aside for this recipe.
Use whole organic milk, the fattier the better for a thick yogurt. You can use raw unpasteurized milk too (but only if you are used to work with this milk)
Use plain store bought yogurt or yogurt from a previously made batch. The yogurt from the store should have life cultures mentioned on the label.
I flavored my yogurt with vanilla, you can flavor yours with powdered fruits too or chocolate powder.
I prefer to work with a yogurt maker but the oven technique works well too.