For making filling : Heat oil in a karahi and put cumin seeds and when cumin seeds splutter put finely grated ginger. Saute for 30 seconds. Add peas. Again sauté for 30 seconds. Add salt, red chilli powder, turmeric powder, garam masala, coriander seeds powder and mango powder. Mix well. Now add mashed boil potatoes and sauté for 2 minutes while stirring.. Add chopped coriander leaves. Filling is ready Swith off the flame.