The mass-produced chicken tikka sandwich is engineered for the chiller cabinet, and that constraint shapes every decision in it more than the spice does. This is the version that sits in a sealed wedge pack on a meal-deal shelf, made hours before it is eaten and built to survive that wait without the filling weeping into the bread or the bread going to paste. It is the same sandwich as the made-fresh tikka build in name only. Where a counter version is assembled to be eaten in minutes, this one is assembled to be assembled in seconds, by the thousand, and to still hold its shape at the bottom of a bag at half past one.
The craft here is shelf stability run as a recipe. The tikka is diced small and folded into a thick mayonnaise-based dressing carrying the spice, partly for flavour and partly because a bound, emulsified filling holds moisture against the bread for hours where a loose one would soak through by lunch. Salad is minimal and often omitted, because lettuce in a sealed pack wilts and weeps and is the first thing to make a chiller sandwich fail. The bread is a soft farmhouse-style slice chosen for how slowly it stales under film, buttered or spread edge to edge as a deliberate moisture barrier rather than as seasoning. The whole wedge is cut on the diagonal and packed tight so the two halves brace each other and the filling cannot migrate. Eaten cold straight from the fridge, which is how it is designed to be eaten, it should taste evenly spiced from corner to corner, because the entire point of the format is consistency rather than peak.
The variations are the rest of the chiller range and the fresher relatives it stands in contrast to. Chicken tikka and mango chutney sweetens the same pack; chicken tikka and raita cools it; the chicken tikka wrap rolls it instead of layering it; the counter-built tikka sandwich trades shelf life back for being eaten hot and soon. Each deserves its own article rather than being crowded in here.