The Monster Munch sandwich is a crisp sandwich with a specific brand doing the structural work, and the crunch is the entire argument. A handful of Monster Munch, the puffed corn snack moulded into hollow claw shapes, usually the pickled onion flavour, is laid on soft buttered white bread and pressed down until the pieces fracture. The whole point is the contrast that nothing else delivers: a brittle, noisy, intensely seasoned corn shell trapped against yielding bread, so each bite shatters before it softens. This is not a filling chosen for substance. It is a texture chosen on purpose, and the bread exists only to frame and trap it.
The craft is timing and pressure. The crisps have to go in dry and be eaten soon, because a corn snack left against buttered bread goes stale and chewy within minutes and loses the only thing it was there for. The bread is deliberately soft and plain so it compresses around the pieces rather than competing with them, and it is buttered to the edges, both to seal the crumb and to glue the loose shapes so the sandwich holds together for the few bites it is meant to last. The press is structural, not optional: it fractures the hollow shells into a uniform crackle and binds them into the butter so the sandwich is a single crisp layer rather than a bag of loose pieces sliding out the sides. Pickled onion is the flavour that carries it because its sharp tang cuts the plain bread the way a pickle cuts a cheese sandwich.
The variations are the snack aisle running the same logic. Wotsits bring a softer cheese-puff crumble; a salt and vinegar or cheese and onion crisp gives a flatter, sharper shard; the plain ready salted version is the crunch with the seasoning turned down. Each is the same branded-crisp, crunch-trapped idea wearing a different packet, and each deserves its own article rather than being crowded in here.