Heat about 1 tablespoon oil in a small frying pan (skillet) over medium heat, add the grated coconut and dried red chillies and stir-fry for about 1 minute, or until the coconut changes colour. Add the turmeric, mix well and remove from the heat.
Transfer the mixture to a blender or food processor and process, without adding any more water, until ground.
Heat the remaining oil in a large frying pan, add the mustard seeds and stir-fry for about 1 minute, or until they start to splutter. Add the green chillies, curry leaves, ginger pieces and coconut pieces and fry for 3-4 minutes.
Add the ground coconut mix to the pan together with the tamarind and season with salt.
Pour in 500ml / 18fl oz (2 1/4 cups) water and bring to the boil. Cook for about 15 minutes, or until the sauce thickens.