Add 8--10 C. water to a wok. Bring to a boil. Poach the fish for about 2 minutes (do not overcook it). Remove the fish to a serving dish. Pour the water from the wok. Sprinkle the scallions, ginger, and black pepper over the fish.
Heat the oil in the wok until smoking hot. Pour the oil over the fish.
Clean the wok. Add the chicken broth; bring to a boil. Add the soy sauce, sweet peas, wine, sugar, vinegar, salt (but taste the sauce before adding any salt), and liquid cornstarch. Stir lightly until the sauce thickens and clears---about TEN SECONDS. Pour the sauce over the fish, garnish with sesame oil, and serve hot.
Variations. For hot and sour fish, add 1 tsp. hot red pepper powder or 1 tsp. hot pepper oil to the sauce when you add the soy sauce.
For sweet and sour fish, add 1--2 Tbsp. sugar at the same point.