Pour the milk into a large deep pan and set over a low heat until it reaches 38C on a thermometer. Remove from the heat, add the yogurt, mix well, then cover with a lid and leave for 25 mins.

Add the rennet, stirring very gently, then cover again and leave for another 15-20 mins.

Remove the lid and check if the curds have coagulated and separated from the whey. Use a large whisk or a knife to break up the curds very gently to create pieces around the size of a hazelnut.

Heat a larger pan half-full with water over a gentle heat to 40C. Put the pan containing the curds into the larger pan to create a bain-marie and check the water temperature frequently to ensure it stays at around 40C. Top up the water from time to time if needed.

After 2 hrs 30 mins, remove the curds from the pan using a slotted spoon and leave to drain in a colander for about 15 mins. Cut the curds into small pieces and put in a large heatproof bowl.

Empty the pan of water, then refill and heat to 85C. Pour the hot water over the curds and mix with a wooden spoon for 30-40 seconds. Strain off almost all the water and again, add water at 85C to cover.

Fold and stretch the curd in the water using the wooden spoon. Keep working until the curds start to become elastic. Now work the curds by folding and stretching by hand (the water will be hot so wear rubber gloves) until they become smooth and elastic.

Take smaller pieces of the curd and shape into balls. Immediately put in a tub of cold water and chill in the fridge. Can be kept in water, covered, and chilled for up to a week.