Ingredients:
Rice (preferably Idly Rice from the Indian Market)
Urad Dal (Black gram lentils also found in the Indian Market)
Salt
Yeast (only if needed)
Water
Preparation:
Day 1 (morning):
Soak 2 cups of rice and 1 cup of urad dal in water for a MINIMUM of 12 hours.
Day 1 (12 hours later):
Blend the rice and dal using a blender to as fine a mix as you possibly can using a minimum of water. (Note: the consistency of the batter should be about the same as that used for pancakes).
Allow the batter to sit at room temperature to ferment (overnight; maybe 8 hours depending on the temperature of the room) Note: If you let the rice and dal soak for at least 12 hours you will not need to add Yeast. If pressed for time you can add yeast just like you would add it to make bread.
Day 2:
After the batter has fermented, add salt to taste.
Warm a griddle up. Spread about half a cup of batter evenly as thin as possible. Sprinkle a little oil around the edges of the dosa and let cook. Add some of the potato filling to the center. Fold either like a crepe or like a taco and serve warm with chutney and sambhar.