First of all take both the flour in a bowl then add in salt, cumin seeds and water as per required and make nice batter from it, consistency of batter should be like of dosa batter.
Now put the batter aside for 1 hour to set, after one hour add coriander leaves and ginger chilli paste in batter and mix well.
Now grease all the banana leaves both the side with oil then put one banana leaf on a non stick tawa, now put 1-2 tsp batter on it and spread it nicely on leaf, make sure that you make a thin layer of batter.
You can put batter more or less as per the size of banana leaf.
Now put another greased banana leaf on batter, press it gently so it can be stuck nicely and cook for few minutes then turn the side and cook other side for few minutes.
Greased oil is enough to cook panki but if you see it is not enough then you can apply more oil while cooking using a brush.
Now check the panki, for checking just remove the upper leaf if it is removed easily then it is cooked or else cook for further few minutes, make all the pankis similarly and serve hot.