recipe adapted from The River Cottage
You don’t have to add the dried milk powder, but it helps to thicken the yogurt. Makes 500ml.
500ml whole milk
25g dried milk powder
3 tbsp live, plain, whole milk yogurt
Put the milk in a saucepan and whisk in the dried milk powder. Place over a medium heat until the milk steams and bubbles appear around the edge. Pour into a warmed mixing bowl and leave to cool until a thermometer reads 46C (or, in the absence of a thermometer, dip in a scrupulously clean finger and if you can keep it there for 20 seconds without causing undue pain, it’ll be about right).
Whisk in the live yogurt, then cover the bowl with a lid or cling film, wrap it in a clean towel and put it somewhere warm – an airing cupboard or above a radiator, say. Alternatively, pour it into a warmed, wide-mouthed Thermos flask.
Check the yogurt after six to eight hours, or leave it overnight. If it’s thickened and looks set, pour it into a clean, airtight container and refrigerate. Homemade yogurt isn’t as thick as commercial brands, so if you prefer a thicker yogurt, strain it through a muslin-lined sieve set over a bowl in the fridge for a few hours.