1. Mix the chorizo, mushroom and tomatoes together and place in the bottom of a greased ovenproof dish.
2. Place the chorizo mix in the dish then the fish on top, tear the basil and add to the dish, cover with a lid and place in the oven for approx. 15 minutes.
3. Remove from the oven, take off the lid and sprinkle on the basil leaves. Serve.