In a wide skillet (use a wide skillet to speed up the process as you have more surface area), melt ghee and add the mango pulp, cook on medium heat until the pulp begins to bubble and thicken, and reduces to half.
Add the grated mawa, mix well, and stir continuously for about 8-10 minutes on medium heat, until the mixture begins to leave the sides of the pan.
Add sugar, and cook further until the mixture leaves the sides of the pan, add the cardamom powder and mix well.
After another 8 minutes of stirring. Take a small portion of the mixture (be careful as it will be very hot), try to form a small ball with your fingers, if it is still very sticky, cook it further 1-2 minutes. Do not overcook the mixture as the fudge will turn hard and chewy.
Transfer to a greased tray, flatten it to about 1/2 inch or desired thickness, sprinkle nuts and press lightly into the mixture. Leave it at room temperature to set for a few hours. Then cut into desired size pieces and serve. Stays good at room temperature for 2-3 days. Store leftovers in the refrigerator.