Wash the 4 dals well and soak them in a large bowl in plenty of water, along with the red chillies for 3 hours.
Wash the rice and soak in water for 3 hours.
After 3 hours, drain the dal and grind to a slightly coarse paste along with soaked red chillies and curry leaves. Use up to 1/4 cup water if required. Remove into a bowl.
Grind the rice to a paste, using a few spoons of water. Mix along with the dal paste in the bowl.
Add salt, finely chopped coriander, black pepper and mix well.
Heat a cast-iron or non stick griddle pan. Using a kitchen paper, smear oil over the pan.
Prepare big sized adais like you would a dosa (as seen in this video), only don't spread them out too thin. You can also make small sized ones using spoonful of batter per adai. You can make 6 of them at one go on a fairly large sized griddle pan.
Keep them warm in a hot box or in an oven on low heat until ready to serve. Ideally these must go straight from pan to plate, for best taste :)