Heat the oil in a frying pan. Cook the fish, skin side down, for 3 minutes. Turn, then cook for a further 3 minutes until cooked through. Season with freshly ground black pepper.
Meanwhile, put the couscous in a large bowl and pour over 200ml boiling water. Cover the bowl with clingfilm and let sit for 5 minutes. Fluff the grains up with a fork, then stir through the lemon zest and juice, the parsley and most of the spring onions. Pierce the packs of broccoli and cook in the microwave on high for 2-3 minutes.
To serve, divide the couscous among plates and top with the fish fillets. Garnish with the extra parsley and remaining spring onions and serve with the broccoli.
Cook's tip: plaice or pollock would also work well in this dish.