Homemade Plain Yogurt

Heat milk in a large saucepan over medium-high heat, stirring frequently, until it is steaming, barely bubbling and registers 180 degrees F on an instant-read or candy thermometer. (Do not leave unattended--it can boil over very quickly.)

Carefully pour the milk into a clean, heat-safe 5- to 8-cup container. Let stand, stirring frequently, until cooled to 110 degrees F. Combine yogurt with 1/2 cup of the 110 degrees milk in a small bowl, then stir the mixture back into the warm milk.

Cover the container and wrap in a clean kitchen towel to help keep it warm. Place in a very warm place (see Tip) and let stand, undisturbed, until thickened and tangy, at least 8 hours and up to 12 hours. Refrigerate until cold, about 2 hours. The yogurt will thicken a bit more in the refrigerator.