In a large bowl, mix 1 cup of rice, 1/4 cup of urad dal, and 1/4 cup of poha (flattened rice). Rinse the mixture thoroughly and soak it in water for 4-5 hours.
Drain the water and grind the soaked mixture into a smooth batter using a mixer or grinder. Add water as needed to achieve a thick, pouring consistency.
Transfer the batter to a large bowl, add 1/2 teaspoon of salt, and mix well. Cover the bowl and let the batter ferment for 8-10 hours or overnight in a warm place.
After fermentation, the batter should have increased in volume and become bubbly. Gently mix the batter.
Heat a non-stick tawa or griddle over medium heat. Grease it lightly with oil.
Pour a ladleful of batter onto the tawa and spread it slightly to form a thick, small pancake. Do not spread it too thin.
Drizzle a few drops of oil around the edges of the dosa and cover it with a lid. Cook for 2-3 minutes until the bottom turns golden brown and the top is cooked.
Remove the set dosa from the tawa and serve hot with coconut chutney and sambar. Repeat the process for the remaining batter.