Heat oil in a pan over medium-high heat. Splutter fennel seeds. Reduce heat to low. Add grated coconut, and fry, stirring continuously, until it starts to change color. Add 3-4 curry leaves, 1 tablespoon ginger paste, 1 tablespoon garlic paste, ½ teaspoon ground turmeric, ground coriander, garam masala, ground black pepper, and chilli powder. Fry, stirring constantly, for 3-4 minutes. Set aside to cool.Once cooled, grind it into a smooth paste. Add a little amount of water, if necessary.

Meanwhile, place prawns, drumsticks, onions, green chillies, ½ teaspoon ground turmeric, tamarind water (discard the hard bits) and salt in another pan. Add enough water to cook prawns, and place it over medium-high heat. When cooked, add tomatoes, and simmer for another 2-3 minutes. Add the ground paste, and mix well. If the sauce is very thick, add more water. Sprinkle asafoetida on top. Simmer for 4-5 minutes.

For tempering, heat oil in a pan over low heat. Splutter mustard seeds and fenugreek seeds. Add dried red chillies, shallots, and curry leaves. Saute, stirring occasionally, for a minute. Remove from flame, and add it to the prawn curry. Stir well. Serve warm with rice or roti.