Pound all the paste ingredients in a mortar with a pestle until you have a fine paste. Or process in a blender, adding
Bring the stock to the boil in a small pot and add the curry paste, tamarind water, sugar and fish sauce, then simmer for 5 minutes. Add the tomatoes and snake beans and simmer for another 2 minutes, then add the salmon and cook for a further minute. Stir through the spinach and basil leaves to serve.