Chicken paste is governed by the same scrape-thin logic as the rest of the paste shelf, and it is the mild, pale member of that row. Cooked chicken is cured, reduced, and pounded with fat and seasoning into a smooth, spreadable paste that keeps in a sealed jar at the back of a cupboard, and the whole design follows from that keeping. A paste built to survive months unrefrigerated is concentrated and salted to a point where a thin scrape across buttered bread is already a full mouthful. Spread it like a filling and it is too salty to eat. Spread it like a stain and it is a sandwich. The paste is the thing you use least of, which is the inverted ratio that defines the entire form.
The craft is the scrape and the butter beneath it. Butter is not optional lubrication here; it is the carrier that drags the paste's salt evenly across the slice and stops a thin smear reading as a smear rather than a flavour. Chicken paste is the gentlest on the shelf, paler and less aggressive than beef or fish paste, so the scrape can be a touch more generous than bloater would ever allow, but the discipline is the same and the bread still does most of the volume. The bread is soft and plain because the paste has no texture of its own and an assertive crust would have nothing to push against. There is no heat, no second layer, no acid: it is assembled cold, cut thin, pressed, and left in a tin until lunch, and it improves slightly for sitting as the paste works into the crumb rather than weeping out of it. Its logic is that a very small amount of something concentrated turns bread and butter into a meal.
The variations are a row of jars rather than a row of recipes. Beef paste is darker and saltier, ham paste leans on its cure, salmon and crab paste carry the potted idea into fish, and bloater paste pushes it to the strong end with smoked herring. The made sandwich, the paste read from the bread rather than the jar, is its own consideration. Each deserves its own article rather than being crowded in here.