For Vadai :
Wash and soak Channa dal for couple of hours.
Then, drain the water and grind it little coarsely ( like masala vadai ). keep aside.
Grind ginger garlic paste along with green chillies and coriander leaves into paste and add it to the ground channa dal.
Add chopped onions followed by saunf, finely chopped vazhai poo / banana flower and the required amount of salt.
Do not add water to the mixture.
Divide the mixture into small equal sized balls, shape them into roundels ( cutlet or vada shape ) and keep aside. ( Instead of round shape, the mixture can also be made into kofta shape too ).
Heat oil for frying and gently drop the prepared shaped vadas.
Deep fry them in batches in a medium flame until it gets cooked and turns crispy.
Once done, remove and keep aside.
For kuzhambu :
Extract juice from the soaked tamarind and keep aside.
Crush cinnamon stick, laung and saunf coarsely using mortar and pestle. Keep aside.
Heat oil in a pan and add the crushed masala along with the bay leaf and curry leaves.
Add finely chopped onions and saute till it gets translucent.
Add ginger - garlic paste and saute till the raw smell goes off.
Now add the chopped tomato and cook till it turns soft and mushy.
Add turmeric powder followed by chilli powder, coriander powder, garam masala powder and salt.
Mix well and add 2 tbsp of water.
Cook till the oil separates from the gravy.
Now add the tamarind extract along with a cup of water.
Adjust salt at this stage and let it boil till the raw smell of tamarind goes off.
When the kuzhambu gets its consistency, garnish with curry leaves and switch off the flame.
Now add the fried vadas and let it soak for sometime.
Serve with hot rice.