1 cm (1/2 inch) piece of fresh root ginger, peeled and grated
finely grated rind and juice of 1 lime
1 teaspoon clear honey
salt and pepper
lime wedges, to serve
Spread the fennel, potatoes and tomatoes over a baking tray, drizzle over the oil, scatter with the fennel seeds and season. Place in a preheated oven, 200°C (400°F), Gas Mark 6, for 25 minutes, turning occasionally, until cooked and lightly charred.
Meanwhile, slash the mackerel skin several times and season both sides, then place on a foil-lined grill rack, skin side up. Mix together the soy sauce, ginger, lime rind and juice and honey in a small bowl and drizzle half of it over the fish.
Cook under a preheated hot grill until the skin starts to crisp. Turn the fish over, drizzle over the remaining soy mixture and grill for a further 2–3 minutes until the mackerel is cooked through and flakes easily. Serve with the roasted vegetables and lime wedges.