The pâté and cornichon finger is an afternoon-tea sandwich, and what defines it is restraint applied to a rich filling. Smooth chicken liver pâté is spread thin on soft brown bread and laid with sliced cornichons, the small sharp gherkins that cut the fat, and then the sandwich is treated the way every tea sandwich is treated: buttered to the edges, pressed, trimmed of its crusts, and cut into fingers small enough to eat in two bites without a plate. The trimming is not decoration. It is the design. A crust would resist a soft filling and the whole point of the form is that nothing in it should resist, least of all against a pâté that is meant to read as delicate rather than heavy.
The craft is balance and moisture control. Liver pâté is rich, dense, and faintly metallic, so the cornichon is structural rather than a garnish: its acid and its crunch are the only thing standing between an elegant bite and a cloying one, and the slices are laid in an even single layer so every finger carries the same correction. The pâté is spread thin for the same reason, because a thick seam would overwhelm thin bread and turn a tea sandwich into something you could only manage one of. Butter spread to the edges waterproofs the crumb against both the fat of the pâté and the vinegar of the cornichon, so the sandwich survives the half hour between assembly and the tray. Brown bread is the convention here because its slight earthiness sits under the liver more comfortably than plain white, which would taste of nothing against it.
The variations stay inside the crustless, restrained frame. A coarser country pâté swaps smoothness for texture; a smear of cornichon or a thread of redcurrant shifts the sharp note; the wider tea canon of cucumber, smoked salmon, and egg mayonnaise keeps the same trimmed, two-bite discipline. Each deserves its own article rather than being crowded in here.