Soak mushrooms for 10 minutes in warm water, drain, and chop. Heat oil in a wok. When it is very hot, add fish and fry until lightly browned. Remove to warm dish and pour off all but 2 tablespoons of oil. Add tomato sauce, pepper, bamboo shoots, and mushrooms. Cook, stirring for 3-4 minutes, until mushrooms soften. Add wine, sugar, salt, and soy sauce and stir mixture for 30 seconds. Return fish to pan and turn it over in the sauce. Dissolve conrstarch in 1 tablespoon water and add to wok. Stir gently just until sauce thickens. Pour onto serving dish and garnish with onions.