Bring 2 cups milk to a boil in a heavy bottom pot. Allow it to boil further for 10 mins on a medium flame. Keep stirring often to prevent the milk solids getting burnt at the bottom.
Meanwhile add pistachios along with saffron to a blender jar and make a slightly coarse powder. Set this aside.
After 10 minutes of boiling the milk, add sugar and continue to boil for another 10 to 12 mins. Keep stirring often to prevent the milk getting scorched at the bottom.
Add corn flour to 1 cup milk and stir well. Make sure there are no lumps.
Lower the flame completely and pour this to the pot. Keep stirring and boil.
Add the nuts powder and cardamom powder. Mix well and make sure there are no lumps.
Pour cream if using and Cook for 6 to 8 minutess more. Keep stirring. Under 8 mins it turns thick. It should be of pouring consistency.
Switch off the stove & Cool this completely. The mixture thickens further upon cooling.
Pour this to kulfi molds, steel cups or Popsicle molds. Cover with a foil and gently insert a ice cream stick.
Freeze overnight. Immerse these in a bowl filled with water for 1 min or rub the moulds in between your palms for 30 seconds.
Gently hold the stick and demould it. Sprinkle chopped pistas and serve kesar pista kulfi immediately.