2 tablespoons pure vanilla extract or 2 vanilla beans, split
3/4 cup organic plain yogurt
Equipment: 4 pint-sized canning jars
Sterilizing 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 the pot. Cover and bring water to a boil over high heat for about 8 minutes. (If you have a good dishwasher, you may opt to forgo sterilizing your jars as long as they are newly cleaned.)
Add the Milk & Vanilla: In a large heavy-bottom stockpot, add the milk. Whisk in the vanilla extract or scrape the vanilla beans into the milk. Combine thoroughly.
Scald the Milk: 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 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.
Cooling 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 the refrigerator to cool and set for at least 3 hours or overnight. Add to your favorite recipes.