Combine your milk with yoghurt starter and mix thoroughly to distribute evenly. Transfer the mix into a well-washed glass jar and seal. Place into your incubating chamber i.e. your oven, dehydrator (or even thermos flask) maintaining temperatures of roughly 45oC. Ferment overnight until your yoghurt has coagulated and is no longer runny. Longer fermentation time will yield a tangier flavour and fuller digestion of lactose.
Will last approximately 2 weeks in the fridge. Frozen milk may also be used, however this will yield a grainier yoghurt.