Whole butterflied mackerel with grilled asparagus recipe

This recipe is mainly cooked on the barbecue – the barbecued mackerel and asparagus are then drizzled in a lemon butter.

Ingredients

4 mackerel fillets (about 400g/14oz each), butterflied, scales removed and pin-boned
2 garlic cloves, finely chopped
2 tbsp chopped fresh thyme
2 tbsp olive oil
sea salt and freshly ground black pepper

To make the mackerel, lay the butterflied fillets on a baking tray and sprinkle over the garlic and thyme. Season with salt and pepper, drizzle with 1 tbsp oil and carefully rub the flavourings into the fish. Cover and leave to marinate in the fridge for 2 hours. Light the barbecue about 30 minutes before you plan to start cooking (or preheat a grill).
To make the flavoured butter, place the butter, shallot, garlic, horseradish, mint, tarragon, fennel, lemon zest and juice in a bowl and season with salt and pepper. Mix thoroughly until evenly combined. Transfer this butter to a saucepan and heat slowly on the side of the barbecue.
To make the potato salad, place all of the ingredients in a bowl and mix to combine. Set aside.
When the barbecue coals are hot, cook the asparagus spears over a medium heat (rather than on the hottest part of the barbecue) for about 10 minutes, or until tender. Remove from the barbecue and keep warm.
Oil the butterflied mackerel and place skin-side down on the hottest part of the barbecue and cook for about 5 minutes. Turn and cook for 3 minutes on the flesh side to finish. (The skin should have lifted, making it easy to turn the fish over.)
Arrange the fish and asparagus on warm plates, divide the butter between them and serve with the potato salad and lemon halves.