The tramezzino misto is less a single recipe than a way of ordering: it means the mixed platter, a stack of the soft crustless triangles in assorted fillings served together rather than one type alone. What defines it is variety held inside one constant frame. Each triangle is the same pillowy white crumb with its crust shaved off and the same mayonnaise bind, but the fillings rotate, cooked ham, tuna, cheese, egg, vegetable, so the eater moves through several flavours in a sitting without any single bread changing. The shared frame is what makes the assortment read as one dish rather than a random pile. The bland, airy crumb mutes and carries each filling equally, the bind seals every slice the same way, and the uniform soft triangle is what lets a tuna build and a cheese build sit on the same plate and still belong together.
Making a misto well is making each component well and matching them. The loaf is a fine soft white sandwich bread, baked that day, the crust shaved off all four sides so only the tender interior is used, and every slice kept under a damp cloth so none stiffens while the others are filled. Each filling is dressed to the same logic: drained and patted so it carries no free liquid, bound with just enough mayonnaise to coat it and to film the inner crumb so the bread is sealed before assembly. That sealing is the real work across the whole platter, because a watery tuna triangle next to a dry cheese one ruins the set. Every filling is mounded toward the middle so each cut triangle stands with a domed centre and a thin pinched edge, and the assortment is arranged so the eater can tell them apart at a glance. A careless platter is obvious: one filling weeping into its crumb, two triangles indistinguishable, the heights uneven so the dome reads only on some.
The variations are really the individual builds that make up the platter, and each is its own thing. There is the cooked-ham triangle, mild and folded against a thin cheese; the tuna triangle, bound flaky and bright; the egg triangle, soft and rich against the bland bread; and the vegetable triangle, dressed lighter for contrast. Each of those is a complete tramezzino in its own right rather than a member of the assortment, and each deserves its own article rather than being crowded in here.