Make the caper mayonnaise sauce. Desalt the capers by rinsing them in running water. Blend them with a spoonful of cold water and gently mix in the mayonnaise. Add the chopped parsley and then some further spoonfuls of cold water to dilute the sauce and make it smoother.
Cut the tuna flesh into cubes and chop small with a heavy knife, then mix with a trickle of oil and orange zest; finally add the ground fennel seeds, bread-crumbs and salt flakes.
Grease a round pastry ring 12 cm in diameter and use it to shape the patty, smoothing the mixture carefully and pressing it slightly. Cook the patty in a skillet or on a smooth hotplate with a little oil, initially with the steel pastry ring to keep its shape, then using a spatula to brown it nicely on both sides, cooking as desired.
Meanwhile, prepare a salad with the fennel cut into julienne strips, the chopped black olives, the parsley, the spring onion in thin slices and the orange peeled to the quick and cut into chunks. Season with a trickle of oil and a little salt. Cut the bun in half, spread butter on the cut sides and brown in a skillet.
Put the base of the bun on a cutting board, add a little caper mayonnaise, then the patty and the fen-nel salad prepared beforehand. Spread the other half of the bun with caper mayonnaise and cover the burger.
“Huge Burger” recipe courtesy of The Artisanal Burger by Mondadori Electa publishing, 2016. Photography: Maurizio de Fazio. Chefs: Antonio Sorrentino and Enzo de Angelis.