Two soups, two very different bowls

Ask for soup in a Scottish kitchen and you could get either of two classics, and they could hardly be less alike. Cullen skink is a thick, smoky, cream-enriched chowder from the Moray coast, substantial enough to be a whole supper. Cock-a-leekie is a golden, gently sweet chicken and leek broth, the sort of thing you are given when you are ill, cold, or home for the weekend. Both are old, both are thrifty, and both were built around what was to hand: smoked fish from a cold sea in one case, an old hen, a bundle of leeks and a handful of dried fruit in the other.

Knowing which one you are making matters, because the techniques pull in opposite directions. Cullen skink wants richness and body; cock-a-leekie wants clarity and restraint. Get that straight in your head and both are straightforward.

Cullen Skink: the chowder of the north-east

The name belongs to Cullen, a fishing village on the Banffshire coast, and to an old Scots word for a broth or essence. The soup is essentially smoked haddock, potato, onion and milk, and it has been made along the Moray Firth for as long as anyone has been writing the recipes down. Traditionally the fish is Finnan haddie, cold-smoked haddock from the Aberdeenshire village of Findon, which is firm, pale and gently smoky rather than acrid.

• Smoked haddock — about 350g for four people, naturally smoked and undyed if you can get it. Undyed fish gives the proper pale, creamy soup rather than a lurid yellow one.
• Floury potatoes — 500g, peeled and cut into chunks. Floury varieties break down and thicken the pot for you.
• One large onion, finely chopped, plus a leek if you like a softer flavour.
• Whole milk — 500ml, with a splash of double cream at the end.
• Butter, white pepper, parsley or chives to finish.

How to make Cullen skink work

Poach the haddock in the milk at the barest simmer for five to eight minutes, then lift the fish out, reserving every drop of that milk — it is the soul of the soup. Flake the fish, checking carefully for bones. Sweat the onion in butter until soft but never coloured, add the potatoes, cover with water or light stock and simmer until they are collapsing.

Now crush a few of the potatoes against the side of the pan with a wooden spoon. That is your thickener; there is no need for flour. Pour in the reserved poaching milk, return the flaked fish, and warm through gently. Add the cream off the heat and do not let it boil afterwards, or it can split. Season with white pepper and taste before adding salt, because smoked fish carries plenty already. Let it sit for ten minutes before serving, with buttered bread or oatcakes. It will thicken further in the fridge, so loosen leftovers with a little milk; it keeps two days, but the texture suffers if you freeze it.

Cock-a-Leekie: Scotland's oldest pot

Chicken, leeks and prunes sounds like an odd trio until you taste it. The prunes give a soft, faintly winey sweetness that flatters the leeks and adds body to the broth, and they have been in the recipe for centuries. Older versions often included beef or bacon alongside the bird, with oatmeal or barley to thicken; rice became common in the nineteenth century. It is traditionally served in two stages — the broth first, then the chicken and prunes as a second course — though most households now put everything in one bowl.

Getting the broth right

• The bird: an older, flavoursome chicken is ideal. A modern one works perfectly well if you poach it gently rather than boil it hard.
• The leeks: four to six, using the white and pale green parts. Slice them lengthways and wash thoroughly — grit hides deep between the layers. Never brown them; sweat them in the pot until glossy.
• The prunes: twelve to sixteen stoned prunes, added in the last twenty to twenty-five minutes so they hold their shape. Soak very dry ones first.
• Rice or barley: about 50g of long-grain rice or a handful of pearl barley. Simmer it separately if you want a clear broth.
• Seasoning: salt, black pepper and parsley, with a squeeze of lemon at the end to lift everything.

Cover the chicken with cold water, bring it slowly to a simmer and skim the surface properly. Add the leeks after the first hour of gentle cooking, then continue for another hour or so until the meat is falling from the bone. Lift out the bird, strip the meat and return as much as you want. Add the rice or barley with the prunes and cook until tender. Skim the fat, taste, and adjust. The broth improves overnight, and any fat will set on top so you can lift it off cleanly.

Serving, storing and the day after

Both soups belong on the table at Burns Night, St Andrew's Day or Hogmanay, but they earn their place on an ordinary wet Tuesday too. Serve Cullen skink with soda bread, brown bread and butter, or oatcakes, and nothing else — it needs no garnish beyond herbs. Cock-a-leekie wants the same bread, a grinding of pepper and perhaps a small glass of something warming alongside.

Cock-a-leekie freezes beautifully and is often better on the second day. Cullen skink does not, because cream and potato lose their texture, so make what you will eat within a couple of days. As a rule of thumb, cook the skink when the weather is wild and you want a meal in a bowl, and the cock-a-leekie when someone needs putting back together. Both are worth knowing by heart.