Originally we ordered yogurt culture from Cultures for Health, but later found out you can just use plain yogurt as a starter. It's taken us a while to perfect our technique, but now that we have, I MUST share this! Here's how to do it:
First, pour a whole gallon of milk into a pot. We use non-homogenized whole milk from Hickory Hill Farms (you can buy it at Earth Fare), but I think any milk will work. Probably the more fat in it, the better, though.
Next, heat it up to 110 degrees. This part is very important. If you heat it up any higher, let it cool down until it reaches 110F again, otherwise when you mix in your yogurt, you will kill the cultures and it won't work. Make sure you stay and continually stir your milk as it heats up so it doesn't burn on the bottom.
Once your milk has reached 110F, remove it immediately from the heat. Prepare your yogurt (between 1/2 - 1 cup) by stirring it until it is nice and smooth. We've found it's easiest to do this by having your yogurt sitting out while the milk is heating up so it's easy to stir. Then, pour it in the milk.
Next, stir it in until it is well mixed - meaning no lumps and looking pretty smooth.
Once it is all stirred in, put the lid on your pot and place in your oven.
Keep in mind that the oven is OFF.
To keep everything nice and warm, you'll want to wrap the pot in towels.
One in the back,
one in the front,
and one over top.
Then shut the door and turn the oven light on.
This whole process, as you perfect your technique, takes about 10 minutes. Do it right before you go to bed. When you get up, take it out of the oven. We've found the best flavor if you get it out after 8-9 hours. Any longer and the yogurt becomes very tart.
When you take it out, it will be very runny. If you like your yogurt really runny, go ahead and store it and refrigerate it. (Update: don't forget to put a bit in a container to save as a starter for your next batch. Just ladle out some after you take it out of the oven and put it in a jar and place it in the fridge till the next batch) At this stage, it's still too runny for our taste, so here's how to thicken it up:
Take a large bowl and put a small bowl upside down inside it. (For a batch this large, we actually use 2 large bowls and divide it up)
Then place a colander on top of that small bowl.
Then you want to lay a cloth on it. I've found that muslin works great, have also heard that coffee filters work well. Something that will allow the whey (liquid) to drain off.
Next, ladle your yogurt into the cloth.
Then you can put it in the fridge and let it strain until it is the consistency you want. We like it nice and thick (Greek style), and that usually takes 3-4 hours of straining (Update: we tend to leave it in all day until it's almost cheese, then put it in a bowl and use a hand mixer to whip it smooth adding a little bit of whey back in to the texture we want). Afterward, put your yogurt in a container (we saved some old 24 oz yogurt containers) and enjoy! You should be able to fill up at least 2 24 oz. containers. Make sure you set aside about 1/2 - 1 cup of your newly made yogurt to start your next batch.
This is EXCELLENT with some honey drizzled on the top. Seriously, one of my favorite foods. I'd eat it all day if I could get away with it.