Heat ghee in a heavy-bottomed pan on medium heat. Add the grated carrots and sauté for 8-10 minutes, stirring frequently, until they soften and cook down slightly.

Pour in the milk and allow the mixture to come to a gentle boil. 

Reduce heat to low and simmer, stirring often, until the milk reduces and the carrots are completely soft and mushy.

Stir in the sugar until dissolved. Sprinkle in the milk powder, whisking well to prevent lumps. 

Continue cooking on low heat, stirring continuously, until the mixture thickens and begins to leave the sides of the pan.

Mix in the cardamom powder. Cook for 2-3 more minutes. To check if it's ready, spoon a little mixture onto a plate; it should hold its shape without spreading.

Immediately pour the hot Gajar Barfi mixture into the prepared tray. Spread it evenly and smoothen the top using a spatula. 

Sprinkle chopped pistachios on top, gently pressing them in.

Allow the Gajar Barfi to cool completely at room temperature for about 2 hours until set. Once firm, carefully lift it out using the greaseproof paper. Slice into neat squares or diamond shapes using a sharp knife. Enjoy!