Heat oil in a pan,add mustard seeds,let it splutter.
Add crushed ginger, garlic, green chillies and curry leaves. Toss for a minute.
Add onions with little salt and saute till it turns soft and translucent.
Add chopped tomatoes when onions starts to brown. Cover and cook on low flame for 2 mins till tomatoes turn mushy .
Keep the flame low and add all the dry spice powders and mix well. Sprinkle little water and mix so that the masalas get combined well
Now add the dry roasted prawns to this and mix well with the masalas.
Saute for 2 mins.add 1 tsp coconut oil on top and sprinkle few curry leaves and close it with a lid and switch off the flame.