1 Carefully scale fish, if needed. If present, remove the head and cut off the fins with kitchen shears.
2 Cut through abdominal cavity and clean thoroughly, then cut fish crosswise about 3 cm (approximately 1 1/4 inches) thick.
3 Peel the onions and cut into very thin strips. Peel and finely dice garlic.
4 Wash and spin dry the spinach.
5 Peel and cut ginger root into very thin strips.
6 Heat half the oil in a large pot. Season fish pieces with salt and place in pot. Cook over medium heat until seared on both sides. Remove and place on a plate.
7 Add onions and garlic to pot and sauté until slightly browned, 5-6 minutes, stirring occasionally. Add spices and sauté for 1 more minute.
8 Pour coconut milk, fish stock and tamarind water into pot and bring to a boil. Cook 3-4 minutes over medium heat.
9 Return fish to pot, cover and cook over low heat until opaque throughout, 5-6 minutes, turning once halfway through.
10 Heat the remaining oil in a skillet and sauté ginger over medium heat for 1 minute. Add spinach and cook for another 2-3 minutes, then season with salt and pepper. Divide spinach among plates, lift fish from pot and stack 2 pieces on top of each plate, then season broth in pot with salt and pepper and spoon some around spinach. Serve immediately.