For the fish, pat the fish fillets dry with kitchen paper. Rub all over with the salt, then set aside for 30 minutes. This helps the flesh to firm up and draws out any excess moisture.
Prepare a steamer. Alternatively, place a steaming rack into a wok or deep-sided pan filled with 5cm/2in of water. (The surface of the water should not reach the rack.)
When the fish fillets have stood for 30 minutes, transfer them to a heatproof plate and scatter over the ginger. Bring the water in the steamer to the boil and place the plate of fish into the steamer (or onto the rack). Cover the steamer or pan tightly with a lid and steam the fish fillets for 4-5 minutes, or until just cooked through.
When the fish has cooked, remove it from the steamer and sprinkle over the spring onions and soy sauce.
Just before serving, heat the groundnut oil and sesame oil together over a high heat. When the oil is smoking, pour it over the steamed fish.
Meanwhile, for the bean curd, heat a wok or large frying pan over a high heat until hot. Add the oil and the yellow bean sauce and stir-fry for 30 seconds.
Add the soy sauce and salt and continue to stir-fry for a further minute. Finally, add the chili powder and continue to stir-fry for 30 seconds.
Carefully pour in the stock (it may spit when it comes into contact with the oil so take care), then add the bean curd cubes and cook for 3 minutes.
Stir in the garlic and the cornflour mixture and cook for a further 1-2 minutes, or until the sauce has thickened.
To serve, divide the steamed fish fillets equally among four serving plates. Garnish with the coriander sprigs. Ladle the Sichuan-style spicy bean curd alongside and garnish with the Sichuan peppercorns. Serve immediately.