Peel potato, slice thickly and keep immersed in water until use.
Heat enough oil in a kadai.
Take besan, rice flour, corn flour, red chilli powder, turmeric, asafoetida, cumin seeds, cooking soda, pepper and salt in a mixing bowl.
Use a whisk to mix well. Add idli dosa batter, enough water to make a thick batter.
Spoon in ghee to it and mix again.
Add 4-5 potato slices drained from water, patting out excessive water from it.
Coat each potato slice in batter and slide gently into hot oil.
Pour hot oil over the top of bajjis to puff it nicely.
Flip and cook more until both sides are golden and crisp.
Drain over paper towel and repeat to finish.