Update: I still make this yogurt a lot, but now I use about 1/3 cup blue agave and a couple of tablespoons of sugar. I also often drain it in coffee filters to make it thicker - more like Greek yogurt. I keep some plain for use in recipes. I've made it with a full gallon of milk, and that works, too - I just have to let it culture longer once I add the Greek yogurt.
We eat a lot of yogurt at our house - we use it in smoothies and top baked oatmeal with it, in addition to eating it for breakfast and snacks. The boys especially love yogurt. Sometimes I think it's Ben's primary source of protein!
I thought I wanted a yogurt maker, but then I learned yogurt is super easy to make in a slow cooker. I made some last night, and this afternoon the boys ate big bowls of and loved it. Lots of people make plain yogurt, but I though vanilla would be a good base: we can add berries, grated pear or apple, or jam to flavor it.
I'm very excited about the possibilities (frozen yogurt in the summer!), and I'm also happy with the short ingredient list: milk, plain yogurt, sugar, and vanilla. And clearly it's much cheaper and creates less waste than those delicious little 6-ounce cups of Yoplait.
If you decide to make the yogurt, keep scrolling past the recipe for some notes and tips.
1 half-gallon whole milk (pasteurized, not ultrapasteurized)
1 container (4 oz. - 6 oz.) plain Greek yogurt (label should show live and active cultures)
3/4 c. sugar (I may use less next time)
2 T. vanilla
Pour milk into slow cooker and cook on low for 2 1/2 hours. Turn off slow cooker and let sit for three hours.
Remove one cup of warm milk from the slow cooker and whisk it with the plain yogurt.
Add yogurt/milk mixture back to the milk. Recover the slow cooker and wrap the whole thing in a warm blanket or put it in your oven with the pilot light on. Leave it overnight or for 8-10 hours.
In the morning, remove one cup of yogurt. It should be very thick, like Greek yogurt or sour cream. Freeze this yogurt; it will be the starter for your next batch and will take the place of the Greek yogurt you used the first time.
Add sugar and vanilla to the yogurt, and chill.
It would be best to start the process around 5:00 p.m. That way you won't have to stay up late to wait for the milk to cool.
You can use artificial sweetener if you prefer, or leave the yogurt plain and add honey or jam to taste.
Be sure milk is not ultra-pasteurized and that yogurt has live and active cultures.
From what I've read, it's best to start with whole milk and then try lower-fat versions if you like. Whole milk sets up best. 2% or lower may require a packet of unflavored gelatin to set up; I'll update this post when I try it.