Put milk in a very large pan and heat slowly to 31 degC.
Add all of the yoghurt.
Stir and bring back to 31 degC then leave for 45 minutes keeping at 29 to 31 degC.
Stir the milk and add lemon juice stirring all the time. Mix the citric acid in a little water and add to the milk. Stir continuously for 1 minute with a whisk.
Leave to stand for 45 minutes maintaining temperature at 29 to 31 degC until a clean break is achieved.
You can start testing after 20 minutes. If necessary, add more lemon juice.
A clean break is when a cut doesn’t heal but fills with green whey.
When a clean break is achieved cut down and across to form ½ inch columns of curd. Leave to stand for 10 minutes.
Stir gently and intermittently for 20 minutes to keep the curds apart.
Then let the curds rest for 5 minutes and they should sink to the bottom.
Remove 1.5 litres of whey with a spoon.
Add back 1.5 litres of water at 55 degC and test that the mixture has a temperature of 38 degC. Gently apply heat if needed.
Stir gently and intermittently for 30 minutes breaking any large lumps of curd.
Then leave to settle for 5 minutes.
Drain off whey until curds are only just covered.
Apply first gentle press. Use the inner pan of the spaghetti pan and two-thirds-fill one of the milk bottles to use as a weight.ave for 45 minutes keeping at 29 to 31 degC
