Preheat the grill to high and line a baking tray with foil, then brush with a little oil.
Peel the garlic clove. Pick and roughly chop the coriander leaves and finely chop the stalks.
Put the fish on the tray. Grind the garlic and coriander stalks to a paste with a pestle and mortar, then stir in the dried spices and 1 tablespoon of oil.
Cover the fish with the herb paste, turn the grill down to medium, then grill for 8 minutes, turning halfway through – it’s done when the flesh is opaque and flakes easily. When it’s nearly cooked, heat up the naan, if using.
Meanwhile, prepare the salad. Trim, separate out and roughly chop the lettuce leaves, trim and roughly chop the spring onions, then deseed and finely slice the chilli. Cut the lemon into wedges.
Toss the coriander leaves, baby gem, spring onion and most of the chilli in a bowl with a squeeze of lemon juice, a splash of oil and some seasoning.
Arrange the salad on a serving plate, place the fish on top, skin-side up, and spoon over the chutney. Sprinkle with the reserved chilli, then serve with the yoghurt, naan and remaining lemon wedges.