The smoked salmon pinwheel holds the filling constant and changes the geometry, and the geometry is the entire point. The components are the familiar tea-tray pair, cold-smoked salmon and cream cheese, but instead of being stacked between two flat faces of bread they are rolled. A slice of brown bread is flattened, spread edge to edge with cream cheese, layered with salmon, rolled up tight along its length, and cut across into short rounds. Each round shows a spiral in cross-section, the bread and cheese and salmon wound into a coil, and that visible spiral is what the sandwich is for: it is built to be looked at on a tea plate as much as eaten.
The craft is in the roll and the cut, where a flat sandwich is forgiving and this is not. The bread has to be soft and is usually rolled with a pin or pressed thin so it bends into a tight cylinder without cracking along the outside of the curve, since a split there unwinds the whole spiral. The cream cheese is spread firm and completely to the edges because it is the glue that holds the coil shut, and a gap at the seam means a round that falls open on the plate. The salmon is sliced to translucence and laid in an even sheet so the spiral reads as clean bands rather than a smear, and the finished roll is usually chilled before slicing so the cheese sets and a sharp knife can cut clean rounds instead of crushing them. The flavour logic is unchanged from the flat version; only the assembly has been made to perform.
The variations stay inside the rolled format and change what is wound into it. A thin layer of dill or chive in the cheese adds a green band to the spiral. Cucumber laid along the bread before rolling brings a cool crunch and a second colour to the cross-section. The same roll-and-slice technique carries other delicate fillings onto the tea tray entirely. Each deserves its own article rather than being crowded in here.