In a large saucepan, combine the milk powder and water, stirring thoroughly.
Heat the mixture until it reaches a boil, stirring occasionally, then turn off the heat.
Allow the milk to cool until it reaches a lukewarm temperature around 110°F to 115°F (43°C to 46°C).
Just before making the yogurt sterilize the bowl and mixing spoon. To sterilize the bowl and spoon, pour some boiling water into the bowl and over the spoon, then discard the water.
While the bowl is still warm, add 2 tablespoons of natural plain yogurt to the warmed bowl.
Then add the milk, but before doing so, remove any milk skin that has formed on top. When pouring the milk into the bowl use the sterilized spoon to stir the yogurt into the milk.
Next, cover the bowl tightly with plastic food wrap and wrap it with several layers of clean tea towels or towels.
Preheat the oven on low heat for 2-3 minutes until it is just warm, and turn it off. Then carefully place the covered bowl into the oven.
Leave the yogurt undisturbed for 5 hours in the oven and allow it to set. After 5 hours, the yogurt should be thick and ready.
If you see a liquid layer on top of the yogurt this is whey, you can either mix it back into the yogurt or spoon it off.
Transfer the yogurt to a storage container and refrigerate it.