Slit the bitter gourd in half lengthways and de-seed, then cut into 2.5-cm / 1-inch pieces. Place on a tilting tray (roasting pan), sprinkle with salt and, set aside for 30 minutes.
To make the spice paste, heat the oil in a frying pan (skillet) over medium heat, add all the ingredients except the ground spices, and fry, stirring constantly, for about 2 minutes, or until the coconut turns brown.
Remove from the heat, stir in the ground spices and transfer to a small blender or food processor. Add 250ml / 8floz (1cup) water and process to make a smooth paste.
Heat 1 tablespoon oil in a large, heavy-based pan over medium heat, add the bitter gourd, shallots, and green chillies, and fry for a few minutes, or until the bitter gourd is well browned.
Add the tamarind extract and stir in the spice paste. Season with salt and pour in 250ml / 8fl oz (1 cup) water. Bring to the boil and cook for 10 minutes, then remove the pan from the heat.
To make the tempering, heat the oil in a small frying pan (skillet) over medium heat, add the mustard seeds, and stir-fry for about 1 minute, or until they start to splutter. Add the dried red chillies, and stir-fry for a few moments.
Add the remaining ingredients and fry for about 3-4 minutes, or until the shallots are browned. Pour the tempering into the curry, stir well and serve.