Combine the bottle gourd, onions, green chillies, ginger and 1½ cup of water in a deep pan, mix well and cover and cook on a medium flame for 10 to 12 minutes or till all the water evaporates. Keep aside. Add the curds, peanuts and salt, mix well. Remove and keep aside. For the tempering, heat the oil in a small pan and add the mustard seeds. When the seeds crackle, add the curry leaves, red chillies and onions and saute on a medium flame for 4 to 5 minutes, while stirring continuously. Pour the tempering over the curds-bottle gourd mixture and mix well. Serve immediately.