For the curd, heat milk to 22-26°C in a saucepan (check temperature with thermometer). “Inoculate” whole milk with sour milk and stir briefly only once. Let stand at this temperature for 30 minutes.
Dissolve rennet extract in cold water and add to milk. Again, stir only once. Let the mixture stand at room temperature (23°C) for about 15 hours. A solid jelly should form. This can be recognized by the fact that whey has formed on the surface.
Cut the mass from the top into 2-3 cm cubes. Cover a bowl with a boiled tea towel and slowly pour the curd mixture onto it. The whey should be poured off first, then the curd.
Drain the cloth and put it in the refrigerator overnight. To do this, it is best to place the cloth, which has been twisted shut at the top, on a sieve and place it on a bowl that will catch the draining whey overnight. The curd is ready.