Pour the milk into the Crock-Pot insert, cover, and heat over HIGH heat for 2 ½ - 3 hours, or until the milk registers 180 degrees F on an instant-read thermometer.

Turn off the slow cooker, cover, and let the milk sit until it has cooled to 110 degrees F. This will take about 2-3 hours.

Add the room-temperature Greek yogurt to the milk and gently whisk it into the milk.

Unplug the slow cooker and wrap it with a bath towel. Let the mixture sit for 10-12 hours (when you open the lid you’ll see that the milk be a little chunky and it will have separated some from the whey).

Place a large fine-mesh strainer or colander over a large bowl. Line the strainer or colander with cheesecloth.

Pour the milk mixture into the strainer or colander. Let the mixture strain for 2-4 hours. The longer you let it strain, the thicker the yogurt will be. I like to strain mine for 2 hours and I end up with 12 cups of yogurt and just over 4 cups of whey.

Transfer the yogurt to an air-tight container and keep it in the refrigerator. The yogurt will keep for 1 ½ - 2 weeks.

When you’re running low on yogurt, use 1 cup of this batch as your starter culture to make your next batch.