Pour the milk into the crock pot and turn it on low. Let sit 2.5 hours.
Unplug crock pot, leave lid on. Let sit for 3 hours.
Ladle out a bit of the milk and stir it in with the yogurt starter. This yogurt MUST have live cultures. I used nonfat, plain Greek yogurt.
Mix in pudding mix.
Return the mixture to the crock pot and the rest of the milk; stir. Put lid back on and cover with a heavy bath towel or blanket (pot still unplugged). This is its insulator. Leave it like this at least 8 hours.
The longer it sits, the tart-er it gets. I like mine nice and tart.
It will be thin. If you want it thicker, place coffee filters in a colander and drain off whey. You can save the whey for cooking, as it is very healthy!
You can use 2 tbs fat free dry milk or 1 packet plain gelatin in place of pudding mix. I just happened to have pudding mix on hand.
Mix some jam, fresh fruit, etc. into it when you serve. If you don't use vanilla pudding mix, it could also be a great base for dips or sauces.