This is far easier than anyone would believe.
- 1/2 gal whole milk (skim makes runny yogurt, but it works)
- 2 T yogurt (store-bought, or the last 2 T of your last batch)
- Simmer the milk, stirring constantly. Stop when the milk begins to steam, but before it begins to boil (which will radically change the flavor and ruin the yogurt).
- Allow the milk to cool until it is warm – 85 degrees. Test it on your finger.
- Whisk the yogurt in a large bowl until creamy. While whisking, slowly pour in the milk. The danger here is that the hot milk will kill the live cultures in the yogurt, in which case you’ll end up with room-temperature milk instead of yogurt tomorrow.
- Pour the result into yogurt containers, or allow it to set in the bowl. Set in a warm (not hot) spot for 8-10 hours. The timing is not overly important, as set yogurt will not readily spoil at room temperature.