Place a pan, add oil, heat it. Splutter mustard seeds, cumin seeds. Add chana dal, urad dal, curry leaves. Add ginger and saute. Add fresh green chillies. Add chopped onion and saute till translucent. Add salt, turmeric, red chilli powder, sugar and black pepper. Keep flame slow. Mix all well.

Now add the mashed potatoes and give a mix gently. Do not mashed potatoes much. So masala for dosa is ready.

For dosa wash and soak urad dal and raw rice separately in the afternoon. In the night strain the water, wash again. Put rice in the grinder and grind coarsely. Then add the urad dal and grind again till you get a smooth batter. Cover and keep it for natural fermentation. Next day morning your batter is ready.

Condition your tawa. Do not overheat. Put ladle full of dosa batter and make circular dosas. As it dries up, sprinkle oil. Now put potato masala in the centre. Cover from both sides. Serve hot with chutney and sambar.