For the Potato Filling:
Heat ghee in a pan, crush the potatoes into it and mix in the rest of the ingredients.
Toss the potato mixture around for a few minutes till it becomes light brown in colour.
Take it out and keep aside.
For the Dosa:
In a bowl, mash the arbi and mix it with the flour and salt.
Add some water and mix well.
Add the ajwain, red chilli powder, ginger and green chillies and mix again.
Keep adding water and stirring in one direction till the batter turns into a smooth flowing consistency.
Heat a flat pan, dab a bit of ghee on it, pour a ladle of the batter and spread it.
Cook for a few minutes and spread more ghee around the edges to make it crisp.
Then flip it over and cook the other side.
Now put some filling on top and fold the dosa over it.
Serve hot with mint and coconut chutney.
Key Ingredients: Potatoes, clarified butter(ghee), salt, red chilli, ginger, buckwheat flour(kuttu), colocasia(arbi), carom seeds(ajwain), green chillies