Place sago pearls in a colander and place the colander over a large bowl. Wash the sabudana under running water 1-2 times. Using your fingers, gentle move around the pearls and wash thoroughly. At first you will see, very milky water collecting in the bowl, keep going, in about 4-6 minutes, the water will start getting clearer. This method not only cleans the sabudana but also removes excess starch coating the pearls.
Drain the water and add ½ cup of clean water. Set aside for 6-10 hours. The pearls will plump up as they soak. The time of soaking depends on quality of your sabudana, it can take upto 10 hours to become soft. Make sure that after soaking, the tapioca pearls are soft and can easily be squeezed between thumb and finger. Drain the water(if any) after soaking. Set aside.
In a heavy bottomed pot, melt the ghee on low. Add the nuts to it and saute for about 20-25 seconds till you smell the aroma. Take out in a bowl and set aside.
In the same pot, add the cardamom seeds and slowly pour the milk. Set the stove on medium and let milk come to a boil. Reduce the heat to low and let the milk reduce slightly for 10-12 minutes. You will need to stir intermittently to make sure that the milk is not sticking to the bottom.
Once the milk is reduced by ⅓rd, add the soaked sago and immediatley start mixing else the pearls will clump up.
Cook on low - medium heat for another 10-15 minutes stirring periodically till you see that sago pearls have started to become translucent and are cooked through. The kheer will be thickish and have a velvety silk like consistency as you cook it.
Add the saffron milk at this point and mix well. Let cook for another 5 minutes on low till the tapioca are cooked through. Dont make the kheer too thick because it will thicken as it cools.
When the kheer is thick enough(thicken it more than you think, since condersed milk will thin it out),mix in the condensed milk, simmer for another 5 mintues(keep an eye since the kheer gets little sticky) and then take off the stove. Mix in the nuts.
Serve the kheer warm or cold (if desired). It will thicken as it cool down.