Rinse sago well with water and soak sago overnight or for atleast 5 hrs with enough water just to immerse it well...Dont add more water as it will become mushy...just sprinkle little water if you feel its very dry.After the mentioned time if you see the sago must have absorbed the water well and if you press it with your fingers it will be soft, Set aside. Roast peanuts till the skin splutters and brown spots appear here and there.
Discard the skin and grind the peanuts to a coarse mixture.To a mixing bowl - add sago,peanut powder,mashed potato,jeera,ginger,green chilli,lemonjuice,coriander leaves and required salt.
Mix it well until it forms a dough like.Pinch lemon sized ball and shape them into vadas.Make all the vadas ready.
Heat oil - add the sago vadas , carefully turn over and cook till golden brown on both sides.Cook in medium flame to avoid burning.