Soak Kesar/saffron in 1 tbsp hot water for 10-15 mins.
Mash paneer coarsely and mix in condensed milk and milk powder. Heat the mixture in a thick bottom pan. Cook on low - medium heat with constant stirring till the mixture becomes thick and starts leaving the sides of the pan. Remove from the fire and spread onto a greased plate/tray. Make sure you dont spread it too thin. Level it with the back of a spoon or an icing spatula.
Sprinkle cardamom powder (discard the skin and powder the seeds only) and saffron soaked in hot water & top with pista slivers. Refrigerate for a minimum of 45 mins to set. Cut into squares. Keep refrigerated.
Notes
If you are using frozen paneer, soak it in hot water for 20-25 mins, to soften it, so that you can mash it easily. To remove the skin of pistachio, soak it in hot water for 5-10 mins. It's ideal to use a rectangular or square tray/tin for this. I used my swiss roll/jam roll tin. The thickness of the sweet depends on the type of plate/tray you use. You can serve it straight from the fridge. However keeping at room temp for 15-20 mins before serving, will make it more softer. You can store it in the fridge for 5-6 days in an airtight container.