Boil the milk in a heavy bottom sauce pan.
Keep boiling till it reduces to half.
Put the lemon juice and sugar.
The milk should curdle slightly.
Keep on boiling stirring till it becomes one lump and leaves the sides of the pan.
Grease a round or a rectangular dish.
Put the cake in it.
Pat with spatula or hand so that it is uniform.
Cool in fridge for about an hour.
Remove from the tin.
Decorate with pistachios and press a little.
Cut into square pieces and serve.