Cut winter melon or ash gourd into medium-sized pieces and remove their skin. Rinse and thinly grate them, then squeeze out as much water as possible from the pulp and keep it aside.
Into a thick-bottomed pan, add the grated pulp and stir-fry on low-medium heat until all the water content has evaporated and the pulp is soft and 80% cooked. (This can take up to 5 minutes.)
Add 2 tbsp of ghee into the pan, stir to mix it well, and continue sautéing until the pulp starts to melt and come together.
Add cardamom powder(or break-opened cardamom pod) plus jaggery and stir to combine together. Continue to cook for another 2 minutes on low heat.
Meanwhile, heat 2 tbsp of ghee in a small pan on low heat. Add cashews and raisins, fry them for 20 seconds, one after the other, until cashews are light brown and raisins are plump. Turn off heat and pour this over halwa and give it a good mix.
Serve halwa warm. Enjoy!