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Thornback, Boiled
Take a thornback of tolerable size, clean it with scrupulous care, and skin it. Lay in the fish-kettle the part usually eaten, cover it with cold water, and add two ounces of salt and a table-spoonful of vinegar to two quarts of water. Bring the liquor to the boil, skim it well, and let the fish boil gently until the flesh will part easily from the bone, which is a sign that it is sufficiently dressed. Lift the fish out carefully and drain it. Serve on a dish covered with a hot napkin, and garnish with green parsley and sliced lemon. Send melted butter or anchovy sauce to table in a tureen. If liked, the fins of the fish may be fried separately. Time to boil, according to size.
Thornback is skate — Raja clavata, the thornback ray — and the "part usually eaten" is the pair of wings. The whole method is a gentle poach in salted, acidulated water, and the only real skill is judging when to stop.
- What to buyAsk for skate or ray wings, skinned. Fishmongers usually sell them already skinned and trimmed, which removes the messiest step in the original. Allow one 8–10 oz wing per person.
- Freshness is not optionalSkate carries urea in its flesh, which breaks down to ammonia as it ages. A faint ammoniacal smell means the fish is past it; rinsing will not fix it. Fresh skate smells of the sea and nothing else. Skate is often held a day on ice to firm the flesh, but no longer.
- The vinegar is doing workA tablespoon of vinegar to two quarts of water is not seasoning — the mild acid helps counter any residual ammonia and keeps the flesh white. Keep it.
- Salt quantityTwo ounces of salt to two quarts is about 57 g to 2 litres, roughly 3 to 3½ tablespoons of fine salt — a firmly seasoned brine by modern standards. Reduce by a third if you are salting the sauce heavily.
- "Boil gently" means do not boil"Boil gently" -- Bring to a boil, skim, then drop the heat so the surface barely trembles; in modern practice that is a gentle poach rather than a rolling boil. A hard boil shreds the fibrous, fan-like flesh off the cartilage before the centre is done.
- TimingThe book declines to give one, and the doneness cue is sound: the flesh should slide off the cartilage with light pressure from a knife tip. In practice a 1/2-inch wing takes 6–8 minutes, a thick one 10–12. Skate goes from set to woolly quickly.
- Fish-kettle substituteA wide sauté pan or roasting tin across two burners works; the wing should lie flat and be just covered. Lift it out on a wide slotted fish slice or it will break.
- The fried finsThe thin cartilaginous edge strips crisp well in hot fat and are worth doing — flour them lightly and fry at 350F for a minute or two. Serve them alongside as a garnish.
- SauceMelted butter here is the Victorian butter sauce, butter thickened with a little flour and water, not simply drawn butter. Skate is also often served with black butter — butter cooked to nut-brown with capers and a splash of vinegar — which some prefer to anchovy.
- Sourcing noteThornback is among the more commonly landed rays, but several other skate and ray species are prohibited from landing in EU and UK waters. Buy from a fishmonger who can name the species and the fishery.
Skate and ray were cheap fish in Victorian Britain, landed in quantity by trawlers and sold well below the price of turbot or sole, which may be part of why Cassell's gives thornback a plain boiling recipe rather than anything grand. The thornback takes its name from the curved bucklers or "thorns" studding its back, and it was among the most commonly marketed of the British rays. The insistence on cleaning "with scrupulous care" and the tablespoon of vinegar both point at the same problem: skate flesh stores urea for osmotic balance, and it turns to ammonia soon after death, so freshness and acid were the cook's defences. The habit of frying the fins separately survives in the crisp skate-knobs still sold in some English fried-fish shops, and the dish sits alongside the French raie au beurre noir as one of the few classic treatments of a fish that nineteenth-century cookery writers generally regarded as honest, cheap and unfashionable.