Home-made Yogurt (without a yogurt-maker)

I used to make this yogurt very frequently several years ago as did my mum-in-law. This is her recipe:

4 cups water
2 cups powdered milk (whole-milk / skimmed)
4 tablespoons of live yogurt (the heavy Greek yogurt such as Fage is delicious for this)

In a saucepan dissolve the milk powder into the water and bring to the boil. Allow to cool to blood-heat.

Blend the yogurt with a little of the milk then add to the rest of the milk.

Pour into a deep dish (a soup tureen is even suitable).

Cover and keep in a warm place, undisturbed for 5-6 hours until the yogurt has set.
N.B. If using cartoned /bottled milk this should be boiled for at least 2 minutes before using.
Do not disturb the yogurt while it is in the process of setting as this will cause it to separate.