Combine the khoya and powdered sugar in a heavy bottomed pan and cook on a slow flame, stirring continuously till the sugar has dissolved and the moisture has evaporated (approximately 5 to 10 minutes).
Remove from the flame, add the cardamom powder and mix well. Allow it to cool completely.
Divide the mixture into two portions, 2/3 and 1/3.
Add the pistachios to the 1/3 mixture, and mix well.
Add the saffron to the 2/3 mixture, and mix well.
Divide the pistachio mixture into 8 equal portions. Shape into even sized rounds.
Divide the saffron mixture into 8 equal portions and shape into even sized rounds.
Stuff each saffron round with the pistachio round and seal the edges completely and give the shape of modak or use a modak mould to press into desired shape.
Handy Tip: Modak Moulds are available in the market and all you have to do is stuff it with the modak mixture and demould. Do remember to grease the modak mould before use.