Preparation Briskly simmer vinegar, soy sauce, Sherry, and maple syrup in a 9- to 10-inch heavy skillet over moderately low heat until reduced to about 1/3 cup, 20 to 25 minutes. Keep warm. Prepare avocado while sauce reduces: Quarter avocado lengthwise, then pit and peel. Cut lengthwise into 1/2-inch-thick slices, then gently toss together with lemon juice, oil, salt, and pepper in a small bowl. Glaze and bake fish: Preheat broiler. Line a large (15- by 10-inch) shallow baking pan with foil. 3Reserve about one fourth of glaze in a small bowl. Arrange fillets, skin sides down, in 1 layer in baking pan. Spoon about one third of remaining glaze over fillet, then spread with back of spoon to coat evenly. Broil fish 5 to 6 inches from heat, without turning, 2 minutes. Remove pan from broiler and coat with another layer of glaze, then broil 2 minutes more. Remove fillets from broiler and apply a third coat of glaze, then broil 1 minute more (for a total of 5 minutes). Remove from broiler and, with a clean spoon, apply reserved glaze. (Reserved glaze will not have touched uncooked fish.) Divide avocado salad among 4 plates, then serve fish alongside it.
Preparation Briskly simmer vinegar, soy sauce, Sherry, and maple syrup in a 9- to 10-inch heavy skillet over moderately low heat until reduced to about 1/3 cup, 20 to 25 minutes. Keep warm. Prepare avocado while sauce reduces: Quarter avocado lengthwise, then pit and peel. Cut lengthwise into 1/2-inch-thick slices, then gently toss together with lemon juice, oil, salt, and pepper in a small bowl. Glaze and bake fish: Preheat broiler. Line a large (15- by 10-inch) shallow baking pan with foil. 3Reserve about one fourth of glaze in a small bowl. Arrange fillets, skin sides down, in 1 layer in baking pan. Spoon about one third of remaining glaze over fillet, then spread with back of spoon to coat evenly. Broil fish 5 to 6 inches from heat, without turning, 2 minutes. Remove pan from broiler and coat with another layer of glaze, then broil 2 minutes more. Remove fillets from broiler and apply a third coat of glaze, then broil 1 minute more (for a total of 5 minutes). Remove from broiler and, with a clean spoon, apply reserved glaze. (Reserved glaze will not have touched uncooked fish.) Divide avocado salad among 4 plates, then serve fish alongside it.