I was given this idea by a friend of mine, a brilliant chef called Vivek Singh. It works perfectly on the barbecue, under a grill or in the oven and is guaranteed to bring a real "wow factor" to fresh mackerel.

1. Put the Kashmiri chillies for the paste into warm water to soak for 20 minutes while you prepare the fish. Using a sharp knife, carefully score both sides of each fish to create three short, diagonal cuts on each side. With the back of a chopping knife, splat or bruise the lemongrass stalks slightly and insert one into the mouth of each fish, leaving about 5cm (2in) or so sticking out for good effect.

2. Drain the Kashmiri chillies and pat dry. Grind the fennel seeds using a mortar and pestle. Add the turmeric and mustard seeds and mix well. Put these and the other paste ingredients into a food processor and blitz to a thick, fragrant paste. (If you don’t have a food processor, grate the onion, garlic and ginger and chop the chillies and curry leaves finely. Then add the ingredients to a small bowl and stir well to combine.) Remove the paste from the bowl and divide into three equal parts. Set aside.

3. Use two-thirds of the paste to coat the fish on both sides. Set aside for 20 minutes. Preheat the oven to 180 °C (gas mark 4). Put the coated fish on to a baking tray, put in the oven and bake for six minutes. Turn the fish over, then bake for another six to eight minutes until cooked through.

4. To make the relish, put the remaining third of the spicy paste into a saucepan over a medium heat, stirring frequently. As the paste begins to sizzle, allow it to cook for one minute or so, stirring frequently, then add the tomatoes, chilli, salt and sugar, then stir again. Allow it to reduce to a soft dropping consistency, then set aside.

5. Serve each fish with a large dollop of the tomato relish on the side. A green salad and a baked potato make simple accompaniments.