Sauté the pumpkin - heat the ghee in a pan and add the canned pumpkin to this. Sauté over medium high heat for 3-4 mins.
Add the other ingredients - add the condensed milk and ground cardamom to the pumpkin ghee mixture. Mix to incorporate well.
Thicken the halwa - this is probably what takes the majority of the 20 mins. Lower the heat to medium and stir the halwa almost constantly. Scrape down the sides every once in a while and keep mixing it all together. In about 15, or maximum 20 mins, the halwa will come together to be a single mass that becomes slightly harder to move it around the pan.
Garnish with sliced almonds and edible silver foil. Serve warm.
Notes
To add some variation to the recipe, you can use desiccated coconut along with the pumpkin to make it a pumpkin coconut halwa and give it some extra texture.
You could also add ground nuts to this to add more body and extra nutrition.
If you don't have canned pumpkin, you can always use fresh pumpkin in place of canned pumpkin in this recipe. Peel, scoop out seeds and grate the pumpkin before you use it in this recipe.