Soak the rice and urad dal separately in water for 6-8 hours. Add fenugreek seeds along with urad dal.

Rinse and drain the water. Grind the rice, urad dal and fenugreek seeds in a grinder to a smooth batter by adding water as needed.

Add salt and keep the batter for 10-12 hours to undergo fermentation.

Heat oil in a pan. Add mustard seeds to splutter. Add crushed ginger, garlic, green chilli and half of the chopped onion. Fry till onion turns translucent. Add green peas and sprinkle a little salt. Fry till the green peas are half cooked. Next add the mashed potato, turmeic powder, chilli powder and salt. Mix well and cook for a while. Add chopped coriander leaves, turn off the flame and keep aside.

Heat a dosa tawa. Sprinkle little oil and rub with a rubber spatula to spread evenly.

Take 3/4 cup of dosa batter and spread it to a thin round circle on hot tawa. Drizzle a few drops of oil on all sides. Add some portion of the potato mixture in the middle. Sprinkle a little chopped onion, grated carrot, grated coconut and chopped coriander leaves. Allow the dosa to cook till light brown on a low flame.

Fold the dosa and close it. Remove from the tawa and place it on a plate. Make 3 more dosas in the same way with the remaining batter and potato mix.

Serve hot with sambar and coconut chutney.