Add gram flour, rice flour, salt, chilly powder, turmeric powder, carom seeds, asafoetida and baking soda in to a large bowl and mix them well. Now add water and prepare batter without any lumps in it. The consistency of the batter should be same that of dosa batter.
Heat a pan/kadai adding cooking oil enough for deep frying the bajjis. To check the oil is hot enough to fry the fritters, drop a small lump of gram flour batter in it. If the batter raises to the surface immediately, then oil is ready to deep fry the raw banana bajjis. Lower the flame now. Dip each raw banana slice in gram flour batter such that the batter gets coated over banana slice evenly.
Drop them in to oil and fry both sides until they turn light golden color. You can fry the bajjis in batches. Remove the bajjis from oil using perforated ladle and place them on tissue to drain excess oil.
Now serve raw banana bajjis/fritters with spicy coconut chutney and enjoy them as tea time snack.