Peel and cut the bottle gourd into small pieces. Slit green chillies lengthwise.
Heat mustard oil in a non stick pan, add bay leaves, onion seeds, cumin seeds and chillies and saute for 1 minute. Finely chop onion, add to the pan and sauté for 2 minutes.
Add ginger and sauté. Add turmeric powder and salt and mix. Cover and cook for 4 to 5 minutes.
Add prawns and cook till prawns are done and excess moisture evaporates. Add coriander leaves and mix well. Transfer into a serving bowl and serve hot.