Take 1-1/2 litre full fat milk in a pot or kadai. Boil it on high.
Once it comes to a boil reduce the heat to medium. Keep stirring in between.
Boil it until it becomes 1/3 of the total quantity. It should take around 15-20 minutes.
Now add the sugar and cardamom powder to it and mix it well. Boil for another 2 minutes until sugar dissolves.
Turn off the heat and let it cool.
Take 4-5 mangoes of medium size. Wash them.
Cut off the top and keep it aside.
Now insert a knife to loosen up the kernel (guthli or seed). Take it out gently. Put the pulp from the kernel back inside the mango cover.
Now fill the mango with prepared rabri. Cover it with the top we removed from mango.
Place it in a bowl or muffin tray so that mango stands still.
Repeat the same for other mangoes.
Freeze it for 6-8 hours inside a freezer.
Take out the mango and peel it. Cut it into equal sized discs.
Garnish it with pistachio and serve it.