3 tbsp light olive oilPut the sliced carrots in a container that fits them snuggly. Heat the vinegar in a pan with 50ml water to just below a simmer.
Add the sugar, peppercorns, salt, mustard and coriander seeds, stir to ensure the sugar has dissolved and pour the mixture over the carrots. Cover and leave to cool for at least 1 hour, ideally more . Line a baking tray with greaseproof paper. Lay the fish on top, skin side down. Combine the garlic, ginger, masala, oil and a good pinch of salt and spread this over the fish flesh. Refrigerate for 1 hour.
Turn the grill on to its hottest setting, set a shelf 6-8cm from the heat source and close the oven door. Allow the oven to heat up for 10 minutes, turn your extraction fan on, then slide in the tray of mackerel and close the door. Grill for 6-7 minutes, until the spice mix is sizzling and turning golden and the fish begins to release some of its oils. Remove from the oven and allow to rest for 3 minutes.by Ed Smith . Photograph © Issy Croker.