Cheese and Marmite is the cheese sandwich as a deliberate gamble: salt placed on top of salt, with a third thing, yeast, thrown in to see if the stack holds. Marmite is a dark, sticky yeast extract so concentrated and so saline that a thin scrape of it carries more savoury intensity than the entire rest of the sandwich. Laying it against Cheddar, which is itself salty and fatty, is the move that defines this build, and it is a high-risk one. Done with restraint it produces a deep, almost meaty umami the cheese cannot reach on its own. Done heavy-handed it collapses into a single overwhelming hit of salt that buries the dairy entirely.
The craft is the quantity, and almost nothing else. Marmite is scraped, not spread, the thinnest dark film dragged across the bread or, more controllably, mixed into a layer of butter so it disperses rather than landing in concentrated patches. Butter is doing two jobs here: it carries the Marmite evenly and it dilutes it, softening the salt spike so the bite reads as savoury depth rather than a brine shock. The Cheddar is cut thick to hold a register of its own against an ingredient that wants to dominate everything, mature enough that its sharpness still registers under the yeast. Soft plain bread is the right carrier, because any assertive crust would be a third loud voice in a sandwich that already has two.
The yeast-extract slot is where the relatives sit. Bovril swaps the yeast note for a beefy one; a thicker Marmite hand turns the sandwich into a dare; the same extract on plain buttered toast without the cheese is the stripped-back version. Each deserves its own article rather than being crowded in here.