Add grated carrots. Cook on a low to medium flame until all the moisture has evaporated and oil separates from the carrots.
Now add milk powder and mix with the carrots very well. Saute for 1 minute until milk becomes clumpy and looks like khoya.
Now add sugar and mix.
The mixture will loosen up as the sugar melts. Continue to cook on a low to medium flame until the moisture has evaporated and you can see the oil separated from the carrot mixture. Now Turn the flame off.
The mixture will be sticky at this stage due to sugar. This will help the barfi in binding.
Grease a small container with desi ghee and add the barfi mixture. Spread the mixture evenly, pressing gently using a spatula to even out the surface.
Sprinkle some chopped pistachio and press on to the barfi using a spatula.
Let the barfi cool at room temperature. Now cover and refrigerate.