- 1/2 gallon of 2% or whole milk
- 1/4 cup plain yogurt "with active cultures" as a starter
- That's it - yogurt is really simple!
Heat the milk to 180 degrees in a large saucepan over medium to medium-low heat, stirring frequently. If you don't have a thermometer, milk at 180 is just starting to steam but not bubbling. You do not want to overheat the milk, as this will scald it (not good). Carefully pour the milk into a very clean, large glass or plastic jar (it needs to be a least a cup or two bigger than 1/2 gallon, to allow for the expansion of the milk as it got hot). Let it cool on the counter to 115 degrees (this will take around 2 hours, depending on the ambient temperature). For the last half hour of cooling time, let the plain yogurt starter come up to room temperature.
Once the milk cools down, thin out the starter yogurt with some of the warm milk and than mix it back in. Cover and let thicken for 4-12 hours (the longer the culture time, the thicker and more tangy the yogurt). Keep the temperature as close to 115 degrees as possible (less than 105, nothing really happens, but if it gets over 120, you kill the starter cultures). I find that a heating pad set to medium keeps it just right - place the jar and the heating pad in a bucket and pack with towels to keep the pad tight to the jar. I also use plastic wrap to cover the jar and poke a probe thermometer through to constantly monitor the temperature.
Once the yogurt reaches the desired thickness, let cool (unwrapped) on the counter until it comes to room temperature, then chill in the fridge for 8 hours to let it fully set up (I said it was easy, not quick). Once your yogurt has fully set up, you may scoop out of the main curd to serve, but do not try to stir it up (or attempt to "mix in" any whey that weeps out of it). Any additions (such as fruit, granola, etc.) should be gently folded in at service time; the more you mix homemade yogurt, the runnier it gets. However, you can avoid this runniness by turning your yogurt into cheese - but that will have to wait until tomorrow!