Wash the sweet potato really well by scrubbing it and get rid of all the dirt. Peel the skin and discard.
Now grate it using a box grater or a food processor. Keep the grated sweet potato into the bowl of cold water until needed to avoid discoloration.
Heat the ghee in a pan on medium heat. Once hot add chopped almonds and cashews.
Saute with stirring constantly until nuts become lightly golden and toasted. Drain the excess ghee and remove it to a bowl and keep it aside.
In the remaining ghee, add the grated sweet potato. Make sure to drain the water before adding it into the ghee. Saute for 3-4 minutes. You will notice that it is starting to soften.
Now add milk and bring it to a simmer. Continue simmering on low-medium heat for around 8-10 minutes or the milk is thickened. Do stir occasionally to avoid milk sticking and scorching.
Milk is thickened but still not the right kheer consistency. When you take a ladleful of it and pour it back. You will notice that milk and sweet potato stay separated.
Add sugar. Mix and continue cooking for 3-4 minutes.
Add saffron and cardamom powder. Mix and cook for a minute.
Now check the kheer consistency. When you take ladleful and pour it back, you will see both will fall together, no more separation. This is perfect. If yours is not like this, continue cooking for a couple of minutes and then check again.
Turn off the stove and add fried almonds and cashews. Serve this kheer warm or chilled as per your liking.