Soak saffron in the warm milk and set aside. Start the instant pot in saute (normal) mode. Add the moong dal and dry roast for about 10 mins. You want to stop roasting when the color changes to darker yellow or golden.
Add water and stir well. Cancel saute and close lid with vent in sealing position. Pressure Cook on high pressure for 12 minutes. When the instant pot beeps, let the pressure release naturally.
After opening, stir the dal and mash it with the ladle. Now add the ghee, sugar, cardamom and the saffron soaked in milk to the pot. Stir everything well.
Now press the saute (normal) button and keep stirring for about 10 minutes. Make sure to get nice golden color. Halwa is done well when ghee starts to separate. Make sure to scrape the bottom of the pot, so the halwa does not stick to the base
Garnish with chopped nuts. Then take the steel insert out of the instant pot. Transfer to a bowl and serve.