Grind the sugar and the cardamoms to a fine powder and keep aside. To make the paneer, boil milk. After it comes to a boil, take off the fire.
Mix the vinegar with 3 tbsp. water and slowly add to the milk and give a stir. After a few seconds you will notice the milk curdling.
Drain in a muslin cloth and keep under a running tap so that the smell of the vinegar is washed away. Now mash the paneer with the back of your palm for 2-3 minutes.
Then mix the sugar and the rose water and continue to mash for another 2 minutes till it is very smooth and there are no lumps.
Put this mix in a greased steel tiffin box with a lid (in the absence of a lid, use aluminium foil to close the container in which it is steamed). Sprinkle some chopped pistachios over it.
Place the tiffin box in the pressure cooker containing some water in the bottom. Steam without the vent for 5 minutes on high flame and then 10 minutes on low flame. When it cools down a little, refrigerate it. Cut into desired shape and serve.