1 gallon whole milk (not ultra-pasteurized)
140g whole milk powder
¼ cup whole milk Greek yogurt
Place milk in a large pot and heat to 185°F, stirring frequently to prevent a skin from forming and hold for 1-2 min.
Whisk in the whole milk powder until fully dissolved.
Cool the milk to 100-110°F.
Mix in the yogurt, stirring until yogurt is well incorporated.
Incubate at 108°F for 8-12 hours.
Instant pot method: use yogurt setting or sous vide setting.
Traditional method: cover the jar or bowl with a lid, wrap in a moist, warm towel to keep in heat, and place in the oven. Turn on the oven light to keep warm, and let the bacteria do its yogurt making magic for 5 hours.
Chill it in the fridge for at least four hours.
Line a mesh sieve with cheesecloth, and pour yogurt in. Place over a large bowl and let strain in the fridge for a few hours (or overnight), until it reaches a consistency you like.
For Siggi's whole milk, strain only 30-35% of the whey. Aim for 65-70% yield.