Add the milk, the natural yogurt and mix everything for 15 seconds at speed 3.
If you want to add consistency or creaminess, especially if you use skim milk instead of whole milk, add the cream, agar-agar, gelatin or powdered milk according to your preference and quantity. Do not overdo it, remember that they will not thicken when added if not after fermenting.
Program 5 minutes at 45ºC. If the milk is cold from the fridge, add an extra couple of minutes to bring it to the desired temperature. Meanwhile, if you have decided to use the yogurt maker, the oven, or the pressure cooker, it is time to preheat them.
Let it ferment between 10 and 12 hours depending on the method you have chosen.
Pack, cover and reserve in the fridge until you are going to consume them. Remember that you should do it at most in the next 7 days after preparation.