Cook the potatoes beforehand. boil, peel and cut them to large cubes.
Grind all the ingredients mentioned under "To grind raw" to a coarse paste.
Heat oil in a pan and crackle mustard seeds, urad dal and fry the onions until pink.
further add curry leaves and cubed potatoes followed by freshly prepared masala and salt.
mix everything together and add starch water.
close and cook for 10 minutes on medium heat.
Open after 10 minuets and let it cook until almost dry.
serve hot with rice and curry.