Mix saffron, cardamom and nuts together. set aside.
Take cornflour, sugar, milk and ghee in a nonstick kadai and mix well.
Now put it in on heat and keep on whisking.
It will get thick and and thick and thick. You have to keep on cooking and stiring on medium high heat.
At one stage you will see that the mixture leaves the sides of the pan and comes in one big mass around the spoon.
Now add in 2 tblspn of ghee and rose essence mix well. This whole process will take around 15 to 20 mins.
Now divide the mixture into two, spoon one half in a parchment sheet which is lightly greased with ghee.
Now place another sheet of parchment and roll it using a rolling pin till it is thin to your liking. Remove the parchment and sprinkle with the nuts mix. roll with a rolling pin again so the nuts stick to the halwa. Put this halwa in fridge for 2 hours.
In the other half add yellow food colour and mix well. repeat the same process again.
Now cut it into big squares and arrange it between sheets of parchment.