Place a non stick wok over a flame and let it heat. Now slightly dry roast sago pearls in it. Just roast it to make it's upper surface warm but there is no change in color.
Soak sago pearls in any vessel. Add good amount of water so that sago pearl gets drenched completely. Soak sago pearls for 5 to 6 hours.
Within 5 to 6 hours, sago pearls absorb all water. Separate out the sago with your hands. If you soak sago pearls, after sauteing it for a while, then the sago pearls don't stick to each other. Sago pearl is ready to be cooked.
Cut boiled potatoes in small chunks. Coarsely ground the peanuts. Also, finely chop ginger and green chilly.
Add some oil in a wok and saute cumin seeds into it. Now add curry leaves, ginger, green chilly, sago pearls and 1/2 tsp salt into it. Cook on low flame for 5 to 6 minutes. Don't add water while cooking it.
When sago is cooked sufficiently, add coarsely ground peanuts and chopped potatoes to it. Cook for another 2 minutes.
Sago pearl upma is now ready. Squeeze one lemon to it and add some chopped coriander as well. Serve steaming hot.