Wash the dal and rice in several changes of water. Drain.
Soak in adequate water (1 inch above the dal and rice) in separate utensils for 4-6 hours (In harsh winters, you can soak longer).
Soak the methi seeds separately
1 hour before grinding, wash and soak the poha / avalakki / flattened rice / oval in just enough water.
Grind the Dal first to fluffy, thick dropping consistency. Remove to a bowl
Now grind the rice, methi, poha to 90% smoothness. Add the ground dal and grind once more.
Remove the batter from grinder / mixer to a large bowl. Add the salt, mix well with clean, wet hands for 4-5 minutes.
This mixing with hands aids fermentation.
Close the bowl and ferment overnight (preferably in a slightly warm place). In harsh winters, you may need a little more time to ferment.
The next day, mix the batter lightly. Adjust the batter to pouring consistency (adding 1-2 tsp water) to a portion of the batter.
Heat a tava / cast iron griddle to high-medium. Pour 1-2 ladles and spread the batter smoothly in a circular fashion.
Drizzle oil around the dosa and cook till golden brown. Flip once and remove immediately.
Serve hot with sambhar and chutney.
Repeat with the rest of the batter.
Use ONLy as much as batter you need. Refrigerate the rest as it sours quickly especially in tropical climates.
Variation : You may also stuff this dosa with masala potato filling and serve as masala dosa.