First prepare the red peppers, which can be done up to a day in advance and reheated before serving. Preheat the oven to 200°C Fan/220°C/Gas Mark 7. Heat a large well-seasoned ovenproof sauté or frying pan with a lid over a medium-high heat, then add a splash of oil. When it is hot, add the peppers, season with salt and pepper and sauté for two minutes on each side. Transfer the pan into the oven and roast the peppers, uncovered, for 10 minutes, or until softened.
Place the peppers into a bowl, cover tightly with cling film and set aside for 10 minutes — this makes the peppers sweat so you can remove the skins easily. Transfer the peppers into a sieve or colander in the sink and rinse off the skins with cold running water. The sieve catches all the bits and stops your sink from becoming blocked. Cut the peppers in half and remove the seeds and membranes, then slice them into strips and set aside.
Heat the wiped-out pan over a medium-high heat, then add a splash of oil. When it is hot, add the chorizo and sauté for two minutes, or until oils are released. Now add the onion, garlic and bouquet garni, cover the pan, lower the heat and leave the onion to sweat for two minutes. Add the red pepper strips and continue sweating for a further three minutes.
Pour in the chicken stock, turn the heat to medium-high and leave to simmer uncovered, stirring frequently for 20 minutes, or until the peppers have a jam-like consistency. Stir in the basil and season with salt and pepper. Remove the bouquet garni, set the peppers aside and keep hot while you cook the halibut.
Pat the halibut steaks dry and season them all over with salt and pepper. Heat a well-seasoned sauté or frying pan over a medium-high heat, then add a splash of oil. When it is hot, add the steaks and fry for three minutes before carefully turning over. Add the butter to the pan and continue frying for a further three minutes, basting with the butter, or until the flesh flakes easily.
Remove the halibut from the pan and leave to rest, covered with kitchen foil, for two minutes. Meanwhile, add a splash more oil to the pan. When it is hot, add the Padron peppers and sauté for three minutes, or just until they are tender. Serve the halibut on the red pepper mixture with the Padron peppers.