To prepare sauce cut green onioons and carrots into 2" pieces. Then thinkly slice these pieces into very thin julienne strips. Set aside. Heat oil in a small frying pan. Add garlic and ginger and saute for a minute or two. Add the remaining ingredients, except the fish and stir until sugar is dissolved, and mixture is heated through. Remove from heat. Stir in vegetables and cover.
Meanwhile, steam the fish. In a Chinese steamer place the fish on a greased heatproff plate then in a bamboo steamer over a wok containing boiling water. Cover and steam for 10 minutes, for each inch of thickness. Cover with sauce and serve.