Pour gallon of milk into a large pot (Reserve 1/4 cup of milk for later).
Bring the pot just to a boil, and then turn off the heat immediately.
Let milk cool until the temperature reaches 100 degrees. Remove the film on the top.
While milk cools off, mix 1/4 cup of plain yogurt and the reserved 1/4 cup milk in a separate bowl.
When the cooked milk finally cools to 100 degrees, add in the yogurt/milk mixture. Mix it up gently but thoroughly, then cover the pot with a lid.
Wrap pot in a towel, and leave in your oven with the oven light on only for overnight or 16 hours. When the time is up, presto: you magically have yogurt!!!
You can stop right here and you have regular yogurt, or you can strain it further if you want Greek yogurt. Using a colander-lined with cheesecloth or flour sack towel, start draining your yogurt. The goal is to separate the solid yogurt from the liquid. If it looks like a wet, white blob, you’re doing great.
Every few hours either gently squeeze the cheesecloth or use a spoon to stir the yogurt blob to help it to drain faster.
After about 6 hours you have nice, thick Greek yogurt. Opa!
Pour into Tupperware and chill and transfer to the fridge to chill.
Enjoy plain, or with chopped fruit and honey.
Your homemade Greek yogurt lasts in the fridge for about 2 weeks. If you’re using some of the yogurt as a starter for the next batch, make it within 1 week.