• 600 ml/ 1 pt full-fat milk
• 6 g/ ¼ oz sachet of easy-blend yeast
• 1 tsp caster sugar

Bring the milk almost to the boil, remove from the heat and leave to cool to the point where you put a finger in and it feels warm. Too hot and it will kill the yeast.

Transfer to a bowl or jar and stir in the yeast and sugar. Wrap the jar in a washed J-cloth (keep washing until it is ‘fragrance’-free) and leave at room temperature for 3 days, by which time the fermentation will have soured and thickened the milk slightly.

Use at once or keep in the fridge for a week or so. To make the next batch, take 4 tablespoons of this buttermilk and add it to another pint of scalded, cooled-to-warm milk in exactly the same way and so on ad infinitum.