I typically buy two quarts of plain yogurt at a time because we sweeten it slightly for breakfast, use it in baked goods and also use it like sour cream. Even buying two at a time, sometimes we run low (see 5 and 3 year old boys above with teenager appetites) but I typically always have milk around. Yogurt is so easy to make no matter what you read on google about exacting procedures. You heat up some milk slightly hotter than body temp, inoculate with some remaining yogurt and let it set. Easy.
When I first decided to tackle yogurt making a few years ago I didn't want to front the money for a yogurt maker so I tried a method that has you wrap the glass jar of inoculated warm milk with a towel and tuck it in your oven with either the bulb on or the pilot light. It actually worked and the yogurt was tasty, however the idea of running the oven light for 12 hours just for one jar of yogurt seemed a bit silly. After a little sleuthing I bought this salton yogurt maker from amazon but I paid closer to $16. Yes, it's a glorified heating pad with an inner plastic container and a lid. I quickly chucked the inner plastic container and used a one quart glass canning jar instead.
The canning jar fits perfectly inside and I can make back to back batches or more batches without having to wash some specific container.
Now, this thing is so low tech that it has no off/on switch. You plug it in, it's on. Oh and the lid has a reminder function. Not a timer, you rotate the circle to the hour you need to remember to turn it off and when you walk by the yogurt maker you look at the clock, look at the lid, then remember to unplug it. See, low tech. But it does work well, consumes little energy and is small enough to tuck into a cabinet when not in use.
Making the yogurt is super simple. To make a quart I heat 3 1/2 cups of whole milk (yes, whole milk - don't fear the fat) to about 110 degrees. Any hotter and you kill the microbes in the yogurt starter, any cooler and the microbes will be sluggish. I used to use a thermometer but after a while you get a feel for "a little hotter than body temperature."
While the milk is heating up, grab your starter, or the last 1/2 cup of yogurt left in the container. I use the unsweetened, unmessed with yogurt as a starter. Nothing with gelatin in it and at least buy a brand like Stonyfield, Dannon (plain) or Brown Cow that has microbes still alive and kicking.
Measure out half a cup.
Then, because I can't leave well enough alone I give my yogurt a little boost. We all take a daily probiotic and it's powdered in a capsule.
I open a capsule and mix it into the half cup of yogurt then set it aside.
Once the milk is hot, add the yogurt/probiotic mixture and stir.
Pour the mixture into your clean glass canning jar. Well it was clean until I sloshed milk while pouring.
Gingerly place your very full jar into the yogurt maker, put the lid on and set your fancy little time reminder at the top of the lid for 12 hours. Time can vary but I've found 12 hours to be pretty consistent for my batches.
After twelve hours the yogurt should be soft set. The top surface should be set and it will be slightly matte.
Put a lid on the jar and stick it in the fridge to cool. I typically make a batch in the morning so it's ready by evening and then in the fridge overnight. It may seem like a long time but it's untended and this is very simple.
The next morning break out your frosty jar of yogurt. There's something so wholesome about a glass jar filled to the brim with dairy. Love it.
See the top surface after the yogurt sets?
Since this is homemade yogurt that doesn't have milk powder, gelatin or other additives like commercial yogurt it will be set until you stir it. Then it will be a bit runnier than commercial yogurt. No one in our house seems to mind and if you like it a bit thicker you can always strain it over some cheesecloth. I don't bother unless I'm making tsatsiki.
This is how the kids take their morning yogurt. One likes a hit of maple syrup, drizzle of vanilla and a healthy dose of raisins.
The other likes just raisins, no sweetener. I cringe everytime he asks for this but heck, the kid would live on plain sour cream if I let him. Before one of the kids was diagnosed with nut allergies I loved a bit of plain yogurt with sliced almonds and a drizzle of honey. Or you can swirl in a spoonful of jam.