Soak the channa dal for atleast 2 hours, drain the water and grind them as coarse paste. Meanwhile chop finely the broccoli florets.
To the ground dal mixture, add the chopped broccoli florets, chopped onion pieces, chopped green chillies, fennel seed powder, cumin seeds, asafoetida, curry leaves, chopped ginger, coriander leaves and salt and mix everything well.
Heat the oil in a deep bottomed pan. Take a small ball from the vada batter, flatten them in your palms and drop gently one by one to the hot oil. Fry the vadas in small batches until they get golden color. Drain excess oil by placing them over paper towel and serve hot.