Sterilize the Jars: Fill a large stainless steel pot with two inches of water. Place 4 pint glass Mason or canning jars, plus their lids into pot. Cover and bring water to a boil over high heat for about 8 minutes. (If you have a dishwasher, you may opt to forgo sterilizing your jars as long as they are newly cleaned.)
Scald the Milk: In a large heavy-bottom stockpot, add the milk and warm over moderately-high heat, until it reaches 190°F/88°C. Take off the heat.
Cool the Milk: Let the milk cool on its own or if you’re pressed for time, fill your sink halfway with ice cubes and cold water then place the pot into the sink. Let the milk cool to 120°F/49°C.
Add Culture: Whisk the yogurt starter into the cooled milk until incorporated.
Transfer the Milk: Pour the milk into jars (you can use a funnel if you’re worried about spilling), and seal with lids.
Cool the Yogurt: Place them into a cooler and pour warm water (about 120°F/49°C) into the cooler so that it comes about ¾ of the way up the containers, and leave for 3 hours. Or, leave the yogurts in a warm spot on the counter with a tea towel for at least six hours or overnight. Refrigerate: Place in t
Refrigerate: Place in the refrigerator to cool and set for at least 3 hours or overnight. Add to your favorite recipes.