Wash moong dal and soak in water for 3 hours. Strain dal and grind with hep of mixture grinder.
Preheat ghee in a pan and add ground dal into it. Stir dal constantly and cook on low-medium flame. Color of dal will change on roasting. Ghee starts separating from dal and it smells delicious. Dal is cooked. It take 25 minutes for roasting dal. Remove wok form flame.
Now roast mawa in a nonstick pan and keep the flame low. Now mix moong dal into it. Now prepare sugar syrup for making barfi. Take sugar and 1 cup water in any utensil and place it on flame. When water starts boiling, cook for 1-2 more minutes. Sugar syrup is now ready. (To add color to barfi you can also add some food color in sugar syrup).
Peel cardamom and make powder and cut pistachios thinly. Add them in sugar syrup and mix. Now cook halwa in low flame and stir constantly until it thickens in consistency. Mix cardamom powder into it. Mixture is ready, turn off the flame.
Grease plate with some ghee and pour mixture over it. Spread evenly. Sprinkle chopped pistachios and press them gently. Within 2 hours barfi will get set. Now cut this mixture in square pieces. Moong dal barfi is ready. Store it in air tight container and place it refrigerator. Relish eating it upto for 8-10 days.