See recipe for Chicken Stock. If fillets are thicker than half to 2 cm, carefully cut in half horizontally (as you would an English muffin). Trim each into a neat 10 cm square. Cut off tops and bottoms of peppers to leave a band about 5 cm wide; remove seeds and ribs. Cut two 10 cm long rectangular pieces from each. Cut into 0 cm julienne, leaving pieces grouped in a neat rectangle. Place salmon on an oiled steamer tray or plate. Use a cleaver or knife blade to transfer pepper rectangles to fish, completely covering each fillet. Scatter bamboo shoots over the fish, then sprinkle with black beans, ginger and scallions. In small bowl, stir together soy sauce, chicken stock, white pepper, vegetable oil and sesame oil. Pour mixture over. Steam in covered steamer (making sure that water boils steadily but does not boil away) until just cooked through and opaque, 5 to 8 minutes (timing varies according to thickness of fish). Carefully transfer to serving plate, spoon sauce around and serve immediately.