To make the salsa, pour the sake, or sherry, and vinegar into a non-corrosive saucepan. Cut the chilli almost in half, so it can release its flavour, and add it to the pan with the sugar and saffron. Place the pan over a low heat.
Peel and core the pineapple, removing any eyes, and cut it into 2 cm (¾ in) cubes. As soon as the syrup comes to the boil, add the pineapple and return to the boil, then remove the pan from the heat and leave the pineapple to soften.
Mix together the cayenne pepper, garlic granules, onion powder or granules, oregano, paprika and thyme. Season with black and white pepper, and a pinch of salt if you have used onion powder not granules, then stir in 1½ tablespoons of oil to make a paste.
Cut any skin off the fish then coat them with the spicy paste. Put the salsa over a low heat to warm through.
Lightly grease a ridged, iron grill pan or heavy-based nonstick frying pan and place it over a very high heat. When it is really hot, add the fish and grill for 8-10 minutes, turning them halfway through. The fish will smoke vigorously when they touch the pan – this is part of the ‘blackening’ process.
Serve the blackened fish steaks hot with the warm pineapple salsa, and garnish with basil.