Tools: A pot, cooking thermometer, jars, yogurt maker or heat pad.
Directions: 1: Measure out the milk into the pot. What I did was measure out the milk with the jars we use for yogurt. One should put 1 extra measurement in to account for spilling, and loss of one sort or another. I neglected to do so which led to us having a short jar that we're going to use for our starter next time.
2: Bring the milk to 185° - 200° Fahrenheit. Left is the thermometer we were using, we would like to get a new thermometer in the future to make it easier to position because right now I'm just holding it with pot holders. On the other hand I'm constantly stirring anyhow to keep a skim from forming too much.
In the picture Left here is a picture of the milk at temperature. This is right up at almost 200° F. It's also after I hadn't been stirring properly so you have a bit of a skim which you don't want obviously. At this point comes the real challenge, especially for your first few times. That's keeping the temperature steady in your pot
3: For our purposes we kept the milk at temperature for 30 minutes. I figured out that the point that works for our stove in this temperature and humidity is just above medium low, this will obviously vary for everyone's situation. The general recommendation is 20 minutes, but the longer you keep it at temperature, the thicker the yogurt will be. This is due to more evaporation of the liquids. There are other options that we haven't tried for thickening. What we did do is use whole milk, the greater the fat content in the milk the thicker the yogurt for obvious reasons. Some other options discussed in this link for thickening your yogurt including powdered milk, straining, and sitting which we also did for flavor reasons.
While checking on the temperature of the heating milk every 5 minutes, I had another task I was doing that you don't technically have to do. I boil sterilized all of the yogurt jars. I figured it's something that can't hurt to have done. Essentially what I did was on the other side of the stove I put shallow water in the pan, and boiled it. I put the jars mouth down in the boiling water for 5 minutes before taking them out, and setting them aside upside down before pouring the milk in.
4: After keeping the milk at temperature for 30 minutes, now comes the somewhat frustrating part. Waiting for it to cool to 110° F or below before mixing in the starter. You wait for the temperature to cool so you don't kill the bacteria in the starter yogurt that you need for yogurt making. It was a very long process in the past, so I decided to measure how long this time.
Ending Temperature: 193°
10 Minutes After: 165°
15 Minutes After: 143°
20 Minutes After: 133°
25 Minutes After: 126°
30 Minutes After: 120°
35 Minutes After: 115°
40 Minutes After: 180°
This is part of why some folks actually use an ice bath to drop the temperature faster. I didn't use that, but I probably will in the future. Last night I could just have brought it outside, and it would have cooled just fine.
5: Mix in your starter. Left is the starter we used since we like their yogurt. The recommendation is to mix the yogurt in to a separated cup, and mix that in. I just mixed the starter in to the whole pot, and that worked well enough. It just means you have to stir longer to make sure there are no chunks left. I also after I'd done the mixing fork strained out any skim left and any chunks left.
6: I then poured the yogurt into the jars, but wait! We're not done yet!
7: Cover the jars, and keep warm for at least 7 hours. We kept them out on the counter for about 12 hours which increases the thickness of the yogurt, and the sourness of the yogurt. We like the tangier yogurt so it's a win win for us. We like the very thick and firm yogurt and we figured it can't hurt for our purposes to have it longer. We have a yogurt maker thanks to a generous gift from our wedding that does a great job, but you can also use a heating mat or other method that we won't go into due to lack of experience with it. Suffice to say, overnight seems to work just fine for our purposes.
8: Refrigerate overnight to fully set, and thicken.
The Lady of the House didn't want to wait that long before having yogurt, so she went ahead and dug in, and got some photos of the yogurt. Even without the chilling overnight it came out greek yogurt thick which sounds great to me! You can see Bottom just how thick it came out. It looks good to me though! We tend to mix in jam, jelly, preserves, or something of that nature to give a bit of extra flavor. In this photo because it turned out very sour the Lady of the House put in some brown sugar and maple syrup before eating. Overall it's a time intensive process with the long hands on heat up, and long cool down time, but it is not a difficult process, and well worth the time due to the significant cost reduction. $4.99/half gallon for 6 cups of organic yogurt instead of the cost per cup of yogurt seems like a fairly good trade off to me, especially to get exactly what we want after some experimentation.