Heat oil in a pan, add in mustard, urad dal, asafoetida and curry leaves. Let them sizzle.

Add in ginger and saute for a min.

Add in onions, carrots, chillies and saute well.

Add in salt and turmeric powder. Mix well.

Add in some water and bring it to a boil.

Add in mashed potatoes and mix well.

Throw  in the coriander leaves and mix well. Masala done.

Now to make dosa, spread dosa batter thinly, spoon in some butter and schezwan sauce. Spread it evenly. Spoon potato filling over it, let it crisp up, fold from both sides.

Serve.