Have ready an ice-water bath in the sink. Carefully remove the lid and check the milk temperature with an instant-read thermometer. If it is not 180°F (82°C), press the Cancel button to reset the program, then select Sauté and heat until the milk temperature reaches 180°F (82°C). Transfer the inner pot to the ice-water bath, then stir the milk until it cools to 110°F (43°C), about 10 minutes. Transfer 1 cup (240 ml) of the milk to a small bowl, whisk in the yogurt until smooth, then return the milk-yogurt mixture to the pot. Whisk until blended.