Combine the sugar and cornstarch in a small saucepan. Whisk in 1/4 cup of water. Add the remaining ingredients and bring to a boil over medium heat. When the sauce thickens lightly, remove it from the heat. It can be used warm or at room temperature.
Drizzle the lime juice and soy sauce evenly over the fish pieces and let them sit for several minutes. Place the bread crumbs on a plate. Warm 1/4 inch of oil in a large heavy skillet. When a few bits of bread crumbs sizzle merrily and brown quickly in the oil, drain each piece of fish and coat it with the bread crumbs. Saute the fish on all sides until the bread crumbs are golden brown and the fish flakes, about 5 minutes total. Serve the mahi-mahi immediately with the sauce drizzled over it or on the side for dunking. Serve with Hawaiian Chili Pepper Water for more pizzazz.
American Home Cooking, Broadway Books