Mushrooms and cheese make a tramezzino that runs on earthiness and melt-soft richness rather than salt or smoke. Cooked mushrooms, often button or champignon sauteed down or dressed as a marinated funghi salad, bring a deep savory, faintly woodsy note and a yielding texture. The cheese, a mild soft type or a creamy spread, brings fat, body, and a gentle dairy roundness that wraps the mushrooms' earth. Between two slices of soft crustless white bread with a mayonnaise or oil bind, the pair settles into one cohesive, mellow filling. The mushrooms carry the savor and the moisture; the cheese binds and enriches; the bread is the mild pillowy field that lets both register without competition. They need each other plainly: mushrooms alone would read damp and one-note, cheese alone would read flat and rich, and bare bread would soak the mushroom liquid the moment it was assembled.
A good tramezzino funghi e formaggio starts with mushrooms that have been properly cooked down and then drained, never wet, so their liquid does not flood the crumb. The bread is fresh, soft to a thumb, trimmed clean of every crust. The cheese is spread or layered to do double duty, contributing flavor and helping the bind, while a thin coat of mayonnaise or oil on the inner faces of the bread seals the crumb against the residual moisture the mushrooms still hold. The filling is mounded toward the center so the triangle domes, fullest in the middle, tapering clean to the cut. A sloppy build uses undercooked watery mushrooms and a thin smear of cheese, leaving the bottom damp and the flavor weak; a careful one cooks and drains the mushrooms, lets the cheese carry real body, seals the bread, centers the dome, and cuts a diagonal that holds its cross section.
The close relations each deserve their own article rather than being crowded in here. Swap the mild cheese for a sharp blue and the richness and pungency rebalance the whole sandwich. Add cooked ham to the mushrooms and cheese and the build gains a cured spine that changes its register entirely. Lay in grilled vegetables alongside the mushrooms and the earth note broadens into a fuller vegetable build. Dress the mushrooms with truffle and the savor shifts into a different and more pointed direction. The tramezzino funghi e formaggio is the plain earth-and-dairy baseline, and it is best read on those terms before any of those swaps are made.