Homemade Greek yogurt

This is a very, very simple recipe. If you make it once, you'll probably never be able to justify buying it again. The downside is it takes awhile (the steps take almost no time, the process takes awhile though)

Ingredients and equipment:
1/2 gallon milk (any fat percentage)
Clear gelatin (optional)
Dried nonfat milk (optional)
One 4-10oz container Greek yogurt, plain (any fat percentage)
Slow cooker
Strainer
Large mixing bowl
Paper coffee filters
A candy/meat thermometer (optional)
Containers (at least one small and one larger)

1) Pour milk into the slow cooker. Set the slow cooker on low, and let it run for two and a half to three hours. If using skim milk, you may want to add 3-4 Tbsp of dried nonfat milk (adds creaminess), and a packet of clear gelatin (makes it firmer). Experiment. I personally use 1% and haven't had to use either.
2) Unplug the slow cooker, and let the milk sit untouched for 3 hours. Check the temperature - it must be around 125 degrees F/51 degrees C before you continue.
3) Add the contents of the yogurt container. You don't have to use Greek yogurt, you can use any type. I personally started my yogurt using a container of Dannon plain and a container of Chobani, so it should have cultures from both types of yogurt. Whisk together until well mixed.
4) Wrap slow cooker with one or two large bath towels. Let it sit for at least 8 hours - the longer you let it sit, the more tart the resulting yogurt will be (also, the better set it will be).
5) After you're done letting it set, take the strainer and line it with the paper coffee filters. Putting a drop of water on each one will help hold it in place. Set the prepared filter into the large mixing bowl. Ladle in the yogurt, being sure not to knock aside the filters (this can be a bit frustrating the first time you do it). Put the whole thing in the fridge for the next few hours.
6) Periodically check on it. You will see mostly clear, thicker liquid dripping out of the strainer. This is whey. You can use it for making smoothies, breads - a lot of different uses. I personally poured it into ice cube trays that I have marked off and put them in the freezer.
7) After a few hours of straining, the yogurt will be far thicker. Pour what you can out into the larger container, and then scrape the rest off of the filters using a rubber spatula. You will probably get your hands covered with yogurt. Lick off your fingers.
8) Pour just enough to fill the smaller container (I usually use an 8 oz container from store bought hummus), and put it in the freezer. You can use that as your starter for the next batch of yogurt (the freezing doesn't kill the buggies that turn milk into yogurt) instead of buying more storebought yogurt.
9) Repeat ad infinitum. Brag to your friends about how easy it is to make your own yogurt. And enjoy the cheapness too - never having to buy store bought yogurt again, just some milk and coffee filters!

You can flavor it any way you want; I often use some vanilla extract and a packet of splenda. Or I eat it plain. I've been toying with adding some cocoa powder, vanilla extract, and mint extract to make a chocolate mint yogurt. Your imagination is the limit.

This keeps at least 7-14 days. I've yet to have it go bad, because my girlfriend and I both eat a ton of yogurt so your mileage may vary.

Also, you can make larger batches if you have a bigger slowcooker. I made a batch using 1 gallon of milk over the weekend, but I had to leave it on a little longer than a half gallon. The milk ended up scorching a bit and turning kind of brownish. It doesn't taste bad, but its kind of offwhite now. Usually its a pretty white.

Enjoy!

PS:
Apparently this can also be made vegan friendly. Instead of milk use soy, almond, hemp, or flax milk. Instead of regular yogurt, use Stonyfield Farm O’Soy. I have read that you may need to add sugar - so this may take some experimentation. I'm lucky and don't have any problem with dairy.

PPS: You can also do this with sheep or goat milk if you want!