6 cups room-temperature water
4 1/2 cups powdered milk
3 cups boiling water
1 can sweetened condensed milk (optional)
1/2 to 3/4 cup yogurt to use as a starter.
Mix water with powdered milk. Add sweetened condensed milk (if using) and boiling water. Gently whisk in yogurt. Pour into jars. (this recipe makes about 3 quarts of yogurt - I use old mayo jars to put my yogurt in.) Put into insulated container surrounded by warm water and incubate for 3-6 hours or until yogurt is set. Store yogurt in the fridge.
Just a note if you want to make yogurt by only making it from this recipe, and not visiting my blog, I would highly recommend using full-fat powdered milk. I have had a hard time finding it in the stores in the States but HAVE found it in the "hispanic foods" area (notably at Walmart) under the "Nido" brand, I think it is a Nestle product.
Also, don't be scared of incubating yogurt. What I do is use an insulated container, like an Igloo. I put my (covered) jars into it, and then fill up with water that is about the same temperature as the yogurt mixture (I use about 2 parts cold/room-temp water to 1 part boiling water.) Just make sure your water is not too hot, I go for about a bathwater temperature. Cover it up and let it sit for 3 to 6 hours. Check it after about 3 hours to see if it has "set" yet (it should not look runny when you tilt the jar to the side.) If not, let it sit for another hour and check again.
If you have ANY questions, feel free to ask me! I am by no means a "yogurt expert" but this method has worked well for me for the past 4 years!