This crispy hot vadai is my all time favourite and my grandma makes it really too good and crispy. If made really in a proper way, the Vadai stays fresh for almost two to three days. It should be made really crispy enough. A bit extra spicy makes it a better snack for rainy day. It is a snack for any time and any day.

Ingredients:

Gram Dhal - 1 cup
Thuvar Dhal/Toor Dhal - 1 cup
Pattani Paruppu - 1/2 cup (to give the extra crispness)
Salt
Red chillies - 6 round ones or 8 long ones. If you want a bit more spicy add 1 or 2 more
Hing (Asafodeita) 
Curry Leaves - A few
Oil to fry

Soak  all the dals together in water for about 2 hours. 
Drain the water and let the dhals dry for atleast half an hour. 
Grind the chillies, salt and Hing first and then add the dhals without adding any water.
The batter should not be a nice paste, but it should be coarse. 
Add the finely chopped curry leaves to the batter.
Now make small round vadais about the size of the new two rupee coin (it should also be flat enough if you want it to be crispy). 
Fry them in preheated oil.

While adding the Vadais, you could simmer the stove and then increase the flame, when you are turning over again simmer and let the vadais turn crispy. 

Remove from flame when it is golden brown.

Variations:
When you add finely chopped onions to it, it becomes Masala Vadai, but you cant expect it to be that crispy. 
While making Masal Vadai, you can add, mint leaves and a pinch of saunf, while grinding the dhals and while mixing the onions you could add finely chopped cashewnuts also to give a very extra rich taste.