Combine soy sauce, chicken stock and caster sugar in a small saucepan, stir until sugar dissolves, then simmer until slightly reduced (3-5 minutes). Keep warm.
Place a large steamer basket over a wok of simmering water. Place scallops in a single layer in steamer basket, scatter over ginger, cover with a lid and steam until scallops are just cooked through (2-3 minutes). Transfer to serving plates, spoon over soy mixture, top with spring onion and keep warm.
Meanwhile, heat oil in a small saucepan over high heat until smoking (2-3 minutes), drizzle over scallops and serve hot.
