Marinade mackerel halves in orange zest, juice, onion, vinegar, salt, wine, peppercorns, and bay leaves for one hour.
Boil or bake sweet potatoes and potatoes in skins until tender at 180°C.
Remove skins and pass the flesh through a potato ricer.
Season with salt and pepper, then gradually mix in the egg and flour to create a sticky dough.
Divide dough into eight, roll into 1cm thick cylinders, and cut into 2cm sections.
Roll pieces over fork prongs, compress slightly, and set aside on a floured tray for a few hours.
Combine the salad ingredients in a bowl and toss well.
Boil the vegetable stock in a large pan and add the gnocchi.
Brown the butter in a pan, add samphire, a ladle of stock, olive oil, and sage.
Drain gnocchi once they float, toss in the butter sauce, and top with parmesan.
Fry prosciutto in a non-stick pan until crisp and set aside.
Fry mackerel fillets in the same pan for 2 to 3 minutes per side.
Serve gnocchi with salad, mackerel, and crispy ham.