Warm the milk stirring occasionally till the milk comes up.
Cool the milk to lukewarm.
In a bowl add the curd and spread it to the sides. Crush all the lumps.
Pour the warm milk into the bowl put a lid and set aside in a warm corner undisturbed. The milk will set and form a thick curd in 6-8 hours.
In my place where the temperatures hover around 26⁰C-31⁰C the curd will set fine but where it is cold you may have to cover it with a kitchen napkin. In Delhi, my mother used an old woollen cap to cover the bowl.
In a fine sieve layer with cheesecloth or dispaosable napkins in the form of a T and place over a bowl big enough to hold the sieve.
Spoon the cooled curds on to the cheesecloth, cover and refrigerate for 1 to 2 hours, depending on how thick you want your Greek Yogurt.
Transfer to a bowl or jar the contents of the strainer and use as needed.