Method:
Preheat oven to 400°F. Cut 3 diagonal slits on each side of the fish and stuff them with garlic and ginger. Fill cavity with any leftover garlic or ginger. Season fish all over, including inside the cavity, with five-spice powder, garlic powder, salt and pepper.
Put stock, lemongrass, and star anise into the bottom of a large baking dish. Arrange fish on a rack set inside the dish so that it rests just above the stock. Cook, without turning, until fish flakes with a fork and flesh is opaque in the center, about 30 minutes.
Carve fish into four portions and transfer to plates. Drizzle with juices from the baking dish and garnish with green onions.