Heat the oven to 220C/200C fan/gas 7. Whisk the soy, syrup, wasabi and sesame seeds in a small bowl.
Put all the greens in a shallow baking tray and toss with 4 tbsp water. Put in the oven and cook for 10 mins until all the water has evaporated. Meanwhile, pour boiling water from the kettle over the noodles in a heatproof bowl to cover, then leave to soak while you finish off the traybake.
Once the greens are tender, drizzle over half the soy dressing with another 1 tbsp water and half the spring onions, and toss well. Place the sea bass on top, skin-side up, and pour over the reserved soy dressing. Sprinkle a pinch more sesame seeds over the skins. Cook for 5-6 mins until the fish is cooked through and flaking.
Drain the rice noodles, then tip into one side of the tray and coat in some of the sauce. Drizzle over some extra soy, if you like, before scattering with the remaining spring onions to serve.