Slow Cooker Yogurt

Instructions

• Place four 10-ounce jars in a slow cooker. Fill the slow cooker with water up to 1/3 inch of the jar rims. Remove the jars and set aside.
• Cover the slow cooker and preheat on High for about 20 minutes.
• Meanwhile, pour milk and milk powder into a saucepan and whisk to dissolve. Heat over medium heat until just steaming and a thermometer reads 179 degrees F (82 degrees C), about 10 minutes. Remove from heat and place the bottom of the pan into a bowl of ice water. Cool milk mixture until the temperature drops to 114 degrees F (46 degrees C). Lift the pan out of the ice water.
• Measure about 1 cup milk mixture and pour into a bowl. Stir in yogurt until thoroughly blended. Return yogurt mixture to milk mixture in the pan. Pour milk-yogurt mixture into the 4 glass jars, filling up to 1/2 inch of the rims.
• Check that the water temperature in the slow cooker is no higher than 114 degrees F (46 degrees C). If it is cooler, cover and allow to come to temperature. If it is too hot, uncover and turn off the slow cooker.
• Set filled jars in the warm water; the water level should be up to the level of yogurt in the jars. Cover with a folded dish towel and then with the slow cooker lid.
• Turn slow cooker off. Allow to set for 6 hours, keeping the water at 114 degrees F (46 degrees C) as best you can. Check the temperature with your thermometer after about 2 hours, taking care not to disturb yogurt. If lower than 114 degrees F (46 degrees C), turn the slow cooker to Warm for 10 minutes, then shut off again. Check temperature again at the 4-hour mark and repeat. Do not stir or poke yogurt at all during this time.
• Check yogurt after 6 hours by pressing gently on the top or tipping the jars to see if it is set; it is done when yogurt is firm and there is a thin layer of yellowish liquid on the top.
• Remove the jars from water and dry them off. Top with clean lids and place in the refrigerator.