Wash the sabudana 2-3 times to drain off the excess starch. Soak it for 3-4 hours. Drain the water and leave the soaked sabudana to rest on a colander for 30 minutes.Pat dry the drained sabudana with a paper towel or any absorbent material and add it into a medium size mixing bowl.
Coarsely grind the peanuts in a mixer or food processor. Add it into the mixing bowl. Add the mashed potatoes, ginger, coriander, and green chilly. Add salt as required. Mix well.
Lightly wet your hand or apply little oil on your palms. Divide the dough into equal medium size balls. Take one ball and pat it lightly in the shape of a patty. Repeat this for all the balls.
Heat oil in a deep heavy bottomed pan. The temperature of the oil should be such that a drop of the mixture dropped in the oil comes up at once. Deep fry the sabudana patties on low medium heat till it turns crispy and golden brown on both the sides. Take it out on a plate and drain the excess oil by resting on absorbent paper for 2-3 minutes.
Serve the sabudana vadas hot with green chutney or yogurt.