You start by dissolving quarter of a rennet tablet in 50ml of cooled boiled water. Mix a tablespoon of the live yogurt with 50ml of cow's milk and set aside in a warm place.
Mix the rest of the milks together in a pan and heat to 90F/32C on a low heat, do not over stir the mix. Remove from heat and add the yogurt mixture and stir slowly to mix thoroughly.
Cover and leave for 1 hour. After this time if the temperature has dropped bring it back up to 90F/32C.
Gently add the rennet mixture using an up and down movement with a wooden spoon for a few seconds only. Replace the lid and leave for 12 hours.
Cut the curds in different directions and let it all rest in the pan for 10 minutes then line a sieve with the muslin and pour in the curds and either let the whey drain away or collect in a bowl (useful for scone making or skin softening in the bath!) then tie up the ends and hang over a tap to drain completely in a cool place (or tied to a wooden spoon over a bowl in fridge) for 36 hours. Turn over the curds half way through.
Break up the curds with a fork and add 2 teaspoons of sea salt making sure it is completely mixed in with the cheese.
Make a parcel of the muslin with cheese inside and place a heavy weight on top and plate underneith and leave in the fridge to come together, firm up and flatten out a bit for 12 hours (did tell you this took a bit of time didn't I).
Open the muslin and cut into squares, you can sprinkle with more salt but I found mine quite salty enough so didn't add any more. You can eat it now but I left mine in the fridge for another day to dry out a little.
You can store in fridge and use within 3 days if kept in an airtight container, or you can do as I did and put it in a jar with a few herbs and some olive oil and it will keep in the fridge for up to 3 months as long as it is submerged in oil.