Heat oil in a wok on medium flame. Add mustard seeds, urad dhal and bengal gram. Let it splutter. Add curry leaves and potatoes and mix well. Add all the powders and give a stir. No water is needed.
Add salt to it and simmer the flame. Let it cook. Give a stir occasionally. It takes 25 minutes to roast. Add curry leaves to it.
Garnish it with coriander leaves. Crispy spicy potatoes are ready to serve with any rice.