Lightly roast the pistachios on low heat for about 3-4 minutes. Set aside to cool completely. Grind to a coarse powder (Do not over grind, as it may start releasing fat).
In a deep bottomed pan/kadai (preferably non-stick), heat ghee on medium-low heat, add the condensed milk, almond flour, and ground pistachios.
Add green food color, keep stirring continuously for about 5 minutes, mix well.
The mixture will start leaving the sides of the pan. Add cardamom powder, mix quickly and switch off the heat. Do not overcook the mixture.
Spread the mixture over a greased tray to about 1/2 inch to 1-inch thickness. Sprinkle some slivered almonds and chopped pistachios, press the nuts gently into the mixture. Decorate with silver varak.
Allow it to air dry for 6-7 hours or overnight, cut into desired shapes and store in an airtight container. It stays good at room temperature for 2-3 days, or in the refrigerator for a week.