The smoked salmon sandwich is the baseline the whole smoked-salmon shelf is measured against, and what defines it is how little it is allowed to do. Cold-smoked salmon, thin oily slices carrying salt and a quiet woodsmoke, goes on brown bread with butter, a squeeze of lemon, and a turn of black pepper. That is the entire build, and the restraint is deliberate rather than lazy. The fish is the expensive, assertive, finished thing; everything else is there to frame it without speaking over it. Brown bread is the convention because its faint nuttiness sits behind the salmon instead of fighting it, and the absence of any third component is the point. This is the version cream cheese, chive, and dill are all variations on, and stripping it back to bread and fish and acid is what makes it the type case.
The craft is the restraint a good fish demands and a plain build enforces. There is nothing here to hide a mistake, so each part has to be right: the salmon sliced thin, to translucence, so it folds and layers across the bread rather than sitting as a slab that overwhelms a bite; the bread soft and brown and cut without a heavy crust, since chew with its own argument would fight a filling that has none of its own texture; the butter spread firm to the edges so it seals the crumb against the oil of the fish and carries the salt across to the wheat. Lemon and pepper are the only sharp notes and they go on lightly, because two parts fat and salt with no acid read flat and the citrus is there to lift the smoke, not to dress it. It is cut thin and on the diagonal, a sandwich engineered to be tasted, not filled out.
The variations are the rest of the smoked-salmon shelf, each defined by what is set against or under the same cured fish. Cream cheese turns the plain build into a richer, mortared one. Chive or dill works a herb through. A squeeze of lemon pushed to the front becomes its own lemon-led reading. The pinwheel rolls the same components into a spiral for the tea tray, and a named smokehouse stakes the quality claim on its own water. Each deserves its own article rather than being crowded in here.