Cover the rice and moong dal with water and allow them to soak for at least 2 hours.
Drain the water and put the rice and dal in a blender along with the coriander leaves, chillies and salt. Add just enough water to keep the blades running and to get a batter that's thick enough the coat the back of a ladle, but runnier than a pancake batter (unless you want really thick dosas which I personally don't like)
Heat a well-seasoned cast-iron or non-stick griddle. Once it's hot, scoop up about 1/4 cup of batter in a ladle with a rounded bottom.
Pour the batter into the center of the griddle. Using the bottom of the ladle, quickly spread the batter outward in quick, concentric circles until you have a dosa about 7 inches in diameter.
Drizzle a few drops of oil around the edges of the dosa which helps crisp them up.
When the bottom is golden-brown, flip the dosa and cook the other side around 30 seconds.
Serve hot with
or any spicy, gravied vegetable dish.
Tip: If you dosas don't spread and the batter clumps together instead, your griddle could be too hot. Turn off the heat or sprinkle some water on the surface of the griddle to cool it down and try again.