Ingredients:

• 1 cup – Idli rice 
• 1 cup – Raw rice/ pachai arisi
• 1/2 cup – Whole black gram without skin / ulunthu/urad dal
• 1/2 cup – Poha / aval/ flattened rice
• 1/2 tsp – Fenugreek seeds / vendhayam
• Salt as needed
• Water as needed

Preparation method:

1. Wash thoroughly and soak idli rice, raw rice and flattened rice together in a wide bowl. Same way wash and soak whole black gram and fenugreek seeds together in an another wide bowl. Leave it for overnight or atleast 6 to 8 hours.
2. Grind soaked whole black gram in a wet grinder (I always prefer wet grinding for idli and dosai) until it is light and fluffy by adding water little by little (I use either ice water or ice cubes while grinding) and transfer it to a container.The batter should not be sticky but it should be light and fluffy. I usually grind ulunthu for about 40 mins.
3. Now add soaked rice and aval to the wet grinder and grind it coarsely by adding water little by little for 10 to 12 mins. Rice batter should be little watery than ulunthu batter.Then add ground ulunthu along with required salt to the ground rice and grind for another 5 minutes so that it gets mixed well.
4. Transfer ground batter to a big container for fermentation. Container should have enough room for the batter to ferment. Consistency of batter should not be too thick or too thin. Ferment the batter for overnight or at least 9 to10 hrs.
5. Mix the fermented batter well. Now it is ready for making dosai. If you are not going to use it immediately, then refrigerate the batter.
6. Heat a dosa tawa, take a ladle full of flour and spread it like normal dosai. Drizzle some oil/ghee around the sides and after it is slightly cooked, using spatula (dosai karandi) just rub it all over to make it flat. Once you see golden brown color, fold the dosai as shown in the video. Crispy dosai is ready and serve hot with sambar, coconut chutney and tomato chutney.

Notes:

• The quality of idli rice and black gram/ulunthu is very important. Never stock rice and ulunthu for long, better get it in small quantity or when needed. 
• The duration for fermentation may vary depending on the climatic conditions. In winter it may need longer time and in summer it may require less time to ferment. Always try to keep it in a warm place.
• You need to take out the batter from refrigerator about 30 mins before you make dosai. Mix well once before making dosai.