Wash and soak rice, urad dal and fenugreek seeds in enough water for at least 4–6 hours (or overnight). Drain and grind into a smooth batter adding little water. The consistency should be like pancake batter. Cover and keep aside to ferment for 6–8 hours or overnight until batter rises and becomes slightly airy.

Meanwhile, boil potatoes until soft. Peel, roughly mash or cube the potatoes and keep aside.

Heat oil in a pan, add mustard seeds and let them crackle. Then add cumin seeds, curry leaves, chopped green chillies and sliced onions. Sauté until onions are soft and translucent.

Add turmeric powder, green peas (if using), and cooked potatoes. Mix gently. Add a splash of water (about ¼ cup) to soften the mixture and stir. Add salt to taste. Cook for 2–3 minutes and keep the potato masala ready.

Heat a non-stick tawa on medium heat. Pour a ladle of fermented batter and spread thin in a circular motion to form a dosa. Drizzle ½ tsp oil around the edges.

Cook the dosa until the underside turns golden brown and crisp. Place a portion of potato masala in the centre, fold the dosa and remove from tawa.

Repeat for remaining batter. Serve hot dosa immediately with coconut chutney or sambar of your choice.