Prawn and Avocado

Reach into the chiller at half past twelve, pull a wedge from the rack, and the side window shows pale pink prawns against pale green avocado on malted brown. The slice is cool against the palm, the film fogged faintly with condensation. A made-to-order version at a counter is built differently: ripe avocado sliced or mashed onto buttered brown, a half-squeeze of lemon over it, the small cold-water prawns laid on top in a loose layer with a thin smear of mayonnaise underneath or none at all. Either way the cross-section is two soft cool layers in close conversation, and the build is doing something the plain prawn sandwich beside it on the shelf is not.

What it is doing is wearing the prawn cocktail. The dressed prawn sandwich, shellfish bound in pale pink mayonnaise, descends straight from the wine-glass starter that ruled British dinner tables from the 1960s into the 1980s: cold prawns under a sweet pink sauce on a nest of shredded iceberg. The prawn-and-avocado wedge keeps the prawn and the cool sweetness of that starter, drops the lettuce and the heaviest of the sauce, and slides in the avocado, the soft buttery fruit the same aspirational table had only just learned to buy. Where the plain prawn sandwich leaves the shellfish bare under butter, and the prawn-mayonnaise wedge binds it in dressing, this one answers the cocktail's pink sauce with a green fat instead, and that single swap is why the two sit on separate shelves.

The pink sauce that starter ran on has a name and a near-enough date. Marie Rose, the ketchup-and-mayonnaise blend lifted with Worcestershire, lemon and sometimes a splash of brandy, was popularised in Britain by the television cook Fanny Cradock in the 1960s, with a documented recipe by 1967, though seafood cocktail sauces predate her and the legend tying the name to the salvaged Tudor warship Mary Rose has been firmly debunked by the Mary Rose Trust. Spread Marie Rose through the prawns instead of plain mayonnaise and the avocado wedge tints pink and steps fully back into the prawn-cocktail family; leave the dressing plain or absent and the avocado carries the fat alone, which is the form the shelf settled on.

The fruit is the part that has to be caught right, and it is why a premium version exists at all. A ripe Hass gives gently under a thumb at the stem end for barely a day either side of its window; underripe it reads as cold cellulose against the shellfish, overripe it greys and floods the crumb to a green-brown stain before the wedge reaches a desk. A small lean cold-water prawn brings sweetness and the snap of cold flesh but almost no fat of its own, so the avocado has to land at exactly the right softness or the bite loses its only richness. Prawns stay whole rather than chopped for that snap, the one textural break in a filling otherwise all give.

The wedge has accordingly split into a budget reading and a luxury one. The standard meal-deal triangle sits a few hundred metres of pavement from a Boots or Tesco till, prawns and avocado on brown, separate on the shelf from both the plain prawn sandwich and the prawn-mayonnaise one. Above it the chains run a deliberately upmarket version: Marks and Spencer's premium prawn line leans on larger Atlantic king prawns and a Marie Rose seasoned with Worcestershire, Tabasco and brandy, and its open prawn-cocktail sandwich tops sourdough with avocado and prawns in the chain's Collection Marie Rose, the dinner-party starter rebuilt as an upscale sandwich. The customer reaching past the bare and the bound wedge for this one is choosing the soft-fat reading of a prawn cocktail.

The prawn cocktail on the chilled shelf

The British packaged prawn sandwich begins with Marks and Spencer, which put pre-packed chilled sandwiches into its stores in 1980, the first British retailer to sell the hinged triangular pack now found at every till, with a prawn-mayonnaise filling that rose to become its best-selling line soon after. Prawn and avocado appeared on the same chilled cabinet as the chain widened its range through the 1980s, the soft buttery fruit partnered with the cold shellfish on the same malted brown, and rode the meal-deal bundle that Boots, Tesco and Sainsbury's built out across the late 1990s.

Both halves of the pairing were new money on the British plate at the same moment. Fresh Hass avocados reached supermarket produce sections widely only through the late 1970s and 1980s, supplied first from California and Israel and later from Mexico and Peru, a middle-class fruit by the time it met the prawn on the chilled shelf. Pandalus borealis, the small sweet cold-water prawn the build runs on, was being fished from Norwegian, Icelandic and Greenland waters and shelled at commercial scale by the early 1980s, the same shellfish behind the plain prawn-mayonnaise wedge. The starter that taught Britain to eat cold prawns under sauce had primed the shelf the avocado walked onto.

That starter, for all its dinner-party gloss, was a thoroughly commercial invention too. The prawn cocktail was a fixture of the Berni Inns chain of mock-Tudor steakhouses that dominated British eating out after the war, the prawn-mayonnaise sandwich is the bestselling filling Marks and Spencer makes by its own account across more than forty years, and the prawn-and-avocado wedge is the version that took that same starter, kept its prawn, and answered its pink sauce with a fruit the chains had only just put on the shelf.