Cook the pasta in a large saucepan of boiling water as per packet instructions. For the last minute add the broccoli. Drain and return to the saucepan, along with a couple of tablespoons of the cooking liquid. Keep warm while you cook the fish and make the sauce.
Heat the grill. Lightly oil a baking tray and place the fish on it. Season with salt and pepper. Cook under the hot grill for 5-6 minutes until the fish flakes easily.
Put the cream and stock in a saucepan along with the garlic, chillies, lemon juice and rind and season with salt and pepper. Bring to the boil, reduce the heat and let it simmer for 4-5 minutes. Then stir this mixture and the watercress and parsley through the pasta. Finally flake the fish and gently stir it in.
Serve with a green salad.