Bring the milk to a boil (scald it).

Around 180°.
Stir in 2-4 C powdered milk, cover with lid and let it cool for about 30 min.

When temp reaches 108°-115° pull out a cup, mix your live cultures in and then add it back into your pot.
Turn your oven on warm for 5 min while you wrap your pot in towels to keep the warmth in.

Turn off the oven and turn on the oven light.
Put the pot in the oven and leave for 8-12 hrs.
When done put in containers and let chill for 3-6 hrs depending on the container size.