- 4 cups milk
- 1/4 cup instant nonfat dry milk powder, or more to taste
- 1/2 cup plain kefir
- Preheat a yogurt maker or slow cooker on Low.
- Whisk milk and dry milk powder together in a saucepan over medium heat until almost boiling, about 4 minutes. Cool milk to lukewarm (100 to 110 degrees F/38 to 45 degrees C).
- Gently stir kefir into milk mixture until just blended. Pour mixture into yogurt containers or slow cooker. Cook on Low
- Cook on Low until desired level of tartness and yogurt consistency is reached, 4 to 10 hours. Chill yogurt in the refrigerator, at least 2 hours.