1. Prepare the foil: Preheat the oven to 200°C (180°C fan oven), gas 6. Cut out four 30cm squares of foil and lightly grease with a little oil.
2. Add the parcel ingredients: Put a cod loin in the centre of each square of foil. Scatter over the chorizo and pepper strips, and sprinkle each one with 1/2 tsp vinegar. Season with black pepper.
3. Bake the parcels: Bring up the edges of the foil and fold together loosely to make four parcels. Put in a roasting tin or shallow ovenproof dish, then bake for 25-30 minutes or until the fish is tender and flakes easily.
4. Open the parcels: Serve the foil parcels opened on serving plates and sprinkle with parsley, if you like.