To prepare the potatoes, bring a medium pan of lightly salted water to the boil.
Add the potatoes, return to the boil and cook for about 15 minutes until tender.
To make the gremolata, wash the parsley in cold water and shake dry.
Remove the tough stalks and discard.
Chop the parsley leaves very finely – you should have around 3 tbsp.
Put in a bowl and toss with the lemon zest and juice, garlic and olive oil.
Season with salt and pepper and set aside.
Drizzle 1 tsp of the oil over the fish and turn to coat.
Season all over with a little salt and some freshly ground black pepper.
Wash the fennel and trim to remove any bruised or discoloured parts.
Cut lengthways into three slices.
Put on a plate and drizzle with the remaining olive oil.
Turn to lightly coat.
Heat a griddle pan over a high heat (see tip 2).
Add the fennel and cook for 2-3 minutes until lightly charred then turn over.
Cook on the other side for a further 2-3 minutes until just tender.
Remove and keep warm.
Add the fish fillets to the griddle - skin side down – and cook for 2 ½ minutes.
Carefully turn over and cook for about a minute on the other side (see tip 3).
Drain the potatoes and transfer to a bowl.
Add the oil and crush roughly with a fork.
Stir in the spring onions, lemon juice and seasoning to taste.
Spoon the potatoes into the centre of a warmed plate.
Top with the fennel slices and finish with the cooked mackerel - skin-side up.
Spoon over the gremolata and serve.
1. Buy a fresh mackerel – one about 225g should do. Ask your fishmonger to gut and fillet the fish. Cut the mackerel fillets in half lengthways either side of the pin bones
2. If you don’t have a griddle pan, use a heavy-based non-stick frying pan instead
3. The fish is cooked when a cocktail stick slides easily into the flesh without offering any resistance
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