Ingredients 
Urad dal (black grams without peels) 1 cup 
Rice 4 cups
Salt to taste

Method
Soak the dal  and rice
seperately for 2-3 hours.
Grind it to a smooth batter with very less or marginal water, sepeartely.
Mix both pastes and grind to get a smooth batter.
Add salt to taste and mix well.
Transfer batter to a bigger vessel and allow it to ferment overnight, or atleast 8 hours. 

You can refrigerate after fermentation and can be used for 4 days.