For this dish you need boneless tuna loin, not a steak, which must be very fresh and showing a good rosy to red colour, not a deep meat colour with a metallic sheen. The leftovers are very good for Tacchino Tonnato or Tonno e Fagioli.
Skin the tuna and cut away the dark bloody bits. Rinse and dry. Chop the anchovy, mint and garlic finely, then mix them together. With the point of a knife make incisions in the tuna 6 cm apart and 3 cm deep; fill these incisions with the