Tuna belly may be sliced and served raw, or lightly torched, for sushi or sashimi. Tuna belly also works well for tuna tartare. Pan-searing is the classic method for cooking tuna, but tuna belly can also be grilled, baked or poached. Its striations of fat readily soak up the flavors of marinades.
Mackerel fillets can be broiled, braised, or fried. Its strong flavor plays well against spicy sauces and marinades, but the fish can also stand on its own. The simplest way to cook Mackerel is to season it with salt and pepper and pan-sear 2-4 minutes, skin-side down in a non-stick pan with a small amount of oil until the skin is crisp and golden. Use a weight to keep the ends of the fish from curling.
Squid are best simply cooked: brush with olive oil, sprinkle with salt and lightly char on the grill for about 3 minutes.
Octopus legs are already cooked. To finish them for serving, they only need a quick sear on a grill or plancha, about five minutes on each side, until they take on some char. Brush the legs with olive or avocado oil first, or marinate them in a blend of oils, herbs, and spices.
Whole langoustines may be boiled in heavily salted water for 3-4 minutes. Serve them with a side of aioli for dipping. To grill or broil langoustines, split them in half lengthwise and brush with butter.