Fill a one quart yogurt maker container half full of warm water and dissolve the tbsp of plain yogurt in it. Add the dry milk and mix well. Fill the remainder of the container with water and stir well. Put in your yogurt maker for 6 to 12 hours until it is the desired thickness. Mix the Truvia in when it is done. You may need to drain some water off the top of the yogurt when it is done, so be careful. Store in the refrigerator. For added flavor you can add fruit or sugar free fruit preserves. My favorite is to add sugar free Smucker's blueberry preserves and then stir.