Grilled vegetables give the tramezzino its smoke and its only real challenge: oil. Zucchini, aubergine, and peppers cooked over a flame until soft and charred at the edges bring sweetness, a faint bitterness from the char, and a slick of the oil they were dressed in. Folded between two slices of soft crustless white bread with a mayonnaise or oil bind, that combination has to read as a plate of verdure grigliate without turning the crumb to grease. The vegetables carry all the flavor and most of the moisture. The bread is mild and pillowy and contributes texture and a vehicle. The bind seals the crumb and ties the vegetables into one mass rather than a loose pile that slides apart at the first bite. The two need each other: the vegetables would saturate bare bread, and unbound vegetables would fall out the open side. The balance is the whole craft.
Done well, it starts with vegetables grilled properly and then drained, not dripping, blotted of excess oil so the bread gets flavor without a flood. The bread is fresh, soft to a thumb, trimmed clean of every crust so only the crumb remains. A thin coat of mayonnaise or olive oil is pressed onto the inner faces of the bread, which both binds the build and waterproofs the crumb against the oil the vegetables still carry. The slices of zucchini and aubergine are layered flat and even so they do not slump to one side, the peppers tucked in to fill the gaps, the whole arranged toward the center so the triangle domes and tapers clean to the cut. A sloppy build uses oily undrained vegetables and overfills one end, leaving grease at the bottom and bare bread at the tip. A careful one drains the vegetables, seals the bread, keeps the layers even, and cuts a diagonal that holds its shape.
The close relations each deserve their own article rather than being crowded in here. Add mozzarella to the grilled vegetables and the build gains a creamy element that rebalances the whole thing toward a caprese register. Lay in a slick of pesto with the vegetables and the green note shifts from char to basil. Add a cheese like scamorza and the smoke compounds in a way that warrants separate treatment. Drop the vegetables onto a base of egg salad and you have a different sandwich entirely. The tramezzino alle verdure grigliate is the grilled-vegetable plate transcribed faithfully into soft bread, and it is best read on its own terms before any of those additions.