Put a pan of water on to boil. Line a steamer with baking parchment, add the salmon fillets and scatter with a little of the orange zest. When the water is boiling, add the beans to the pan, put the salmon in the steamer on top and cook for 5 mins. Take the salmon off, and if it is cooked, set aside but add the peas and mange tout to the pan and cook for 1 min more, or if not quite cooked leave on top for the extra min. Drain the veg, but return the boiling water to the pan, add the noodles and leave to soak for 5 mins.
Put the curry paste and fish sauce in a salad bowl with the orange juice and a little of the remaining zest and the spring onions. Drain the noodles when they are ready and add to the salad bowl, toss well, then add the chopped orange with the basil or coriander and the cooked vegetables. Tip in the juice from the fish, then toss well and serve in bowls with the salmon on top.