Combine 2 cups whole milk, 2 cups reconstituted non-fat dry milk and 1/4 cup non-fat dry milk powder in a medium saucepan. Scald, do not boil; remove from heat. Pour into a bowl; cool to lukewarm.

Stir in 2 tablespoons plain yogurt; cover and let stand in a warm place 10 hours. Refrigerate to store. Always save some from batch to start next batch.