The proceeding is really simple: heat 1 litre of milk to 80 °C, then remove from heat and leave to cool down until the temperature drops to 50 °C. Mix two tablespoons of plain white yogurt with live culture or two tablespoons of soya yogurt with live culture into the milk and fill the containers with the mixture up to the 150 ml mark. Attach the lids, put into the thermal insulating bag, close it with the zip closure and leave the yogurt to ferment for at least 6 hours at room temperature. Turn a container upside down to test the yogurt: if the mixture is firm, the yogurt is ready.
Serve chilled; you can flavor it with fresh fruit or juice, marmalade, melted chocolate…