Clean and cut the fish horizontally into 4 pieces, pat dry with a paper towel.
Put salt onto the fish and place them into a dish.
Rinse the salted black beans, drain, and roughly chopped them.
Add the minced garlic and ginger, sugar, and 1 tsp oil to the salted black beans and mix well.
Spoon the mixture evenly onto the fish, and drizzle the rest of the oil over the fish.
Bring some water to a boil in a wok and put the fish onto the steaming rack.
Cover and steam on high heat for 8 minutes.
Sprinkle the green onions over the fish.