Potato Masala / Poori Masala

Potato Gravy / Poori Masala is an excellent side dish for pooris and also goes well with chappathis and dosas. It is a simple but delightful recipe.
Ingredients:
2 potatoes
1/4 tsp mustard seeds
1 tsp cumin seeds
2 tsp channa dal
2 dry red chillies
2 tsp ginger
4 green chillies
1/4 tsp turmeric powder
1 large onion
Curry leaves for garnishing.