Mix milk and powdered milk together in a heavy kettle. Then cover and heat slowly to 180 degrees. Using a heat distributor under the kettle and stirring occasionally will help prevent scorching. Remove from heat and cool to about 125 to 130 degrees.
Then mix about 1/2 cup of the warm milk with 1/2 cup of plain yogurt in a small bowl. Doing this will help assure an even distribution of the yogurt. Then stir this mixture into the kettle of milk. Cover the kettle. Now get a couple of heavy blankets and lay them out nice in a quiet spot on your kitchen counter. Set the kettle in the middle of the blankets and wrap it up well so it retains the heat. You may set a towel under the kettle if you are concerned about spills. Do not disturb for 3-4 hours. then carefully check to see if it is done.
Gently touch the surface with a spoon. If it is firm, or if it is solid but has a bit of clear yellowish liquid on the surface, it is done. Then unwrap it and cool completely before eating. If it doesn't seem done, rewrap and let it set another hour or so. Try not to let it set too long or it tends to get sour, but it is still usable even though you may not like it as well.
This recipe can be reduced in size if 1 gallon sounds like too much. This yogurt has a much more pleasant flavor than plain yogurt from the store. And you may use this yogurt for your starter for your next batch instead of buying another carton.
