Divide milk between two heavy bottomed pan and reduce to 1/3rd.
Now combine both and let it boil. Keep on stirring to avoid the bottom getting burned.
Dissolve citric acid in 2 tbs of water and add it to the reduced milk.
The milk will curdle and whey will be separated.
Add sugar and keep on cooking until the whey completely evaporates.
Add cardamom powder and mix well.
Grease a 6" cake tin with ghee and transfer the mixture to the pan.
Press it well with the back of a spoon until it is firm.
Set aside for 24 hours to set.
For demoulding, place the tin on low heat for a few seconds and flip it onto a plate.
The cake will slide out of the tin.
Slice it up and serve.