In a bowl mix all the dal, wash them changing water 2-3 times. Soak dal in four cups of water for 6-8 hours.
Drain the water. Blend the lentils (dal) with green chili and ginger, adding water slowly as needed to make a smooth batter. Note: The less water, the smoother the batter.
Mix the salt and cumin seeds into the batter. Add water as needed. The total water added will be about ½ cup, just enough to achieve the consistency of pancake batter.
Place a non-stick skillet over medium-high heat. Test by sprinkling a few drops of water on it. The water should sizzle right away.
Pour about ½ cup of the batter mixture into the skillet and spread evenly with the back of a spoon. Starting from the center, spiral outward until evenly spread, about seven inches in diameter.
When the batter begins to dry, gently spread one teaspoon of oil over it. Wait about 30 seconds, then flip the dosa using a flat spatula.
Press the dosa lightly with the spatula all around to ensure even cooking, turning them two to three times. Dosa should be crisp and golden brown on both sides.
Repeat for the remaining dosas.