Scotland's Most Famous Soup

Cullen Skink comes from the small town of Cullen on the Moray Firth coast, tucked between Buckie and Banff in the north-east of Scotland. The name throws people every time, which is half the charm of it. "Skink" is an old Scots word for a broth, originally made from the shin or hough of beef. Along the coast, though, fish was cheaper and far more plentiful than beef, and smoked haddock stepped in to take its place. What resulted is one of the most distinctive soups in the Scottish repertoire, and one that has never really needed improving.

The smoking of the fish was purely practical at first. Before refrigeration, cold-smoking over peat and oak was how the catch was preserved, and the Moray coast had a long tradition of doing exactly that. Arbroath Smokies get all the fame, but the undyed, pale-fleshed smoked haddock from this stretch of coastline has always been exceptional. If you can get hold of undyed smoked haddock from a proper fishmonger, do it. The colour of your soup will be a gentler, more natural cream rather than vivid yellow, and the smoke flavour tends to be a little more subtle. That said, the supermarket dyed kind will still make a very good pot of skink. Don't let sourcing stop you.

The Technique That Makes the Difference

The single most important thing in a proper Cullen Skink is what you do with the milk. You poach the haddock in it first, gently, and that smoky, slightly savoury infused liquid becomes the entire base of the soup. Every bit of flavour the fish gives off goes straight into it. Don't rush this step and don't let it boil. A rolling boil will toughen the fish and can cause the milk to split, and once that happens you're fighting a losing battle. Keep the heat low and patient, watch for the surface to barely tremble, and pull the fish out the moment it flakes easily.

For the potatoes, floury varieties like Maris Piper or Rooster work best. The trick used by cooks who make this regularly is to mash roughly half the cooked potato into the soup to thicken it naturally, leaving the rest in chunks so there's still texture in every spoonful. This gives you a soup that's thick and creamy without being gluey or starchy. Season very carefully at the end, and taste before you add anything. Smoked haddock varies enormously in saltiness and it's very easy to over-season.

Serving and Getting Ahead

Cullen Skink turns up on restaurant menus as a starter, often in quite refined form, but at home it works just as well as a proper main course. A thick slice of crusty bread is the obvious pairing, though oatcakes alongside are very traditional and worth trying. It's one of those soups that genuinely improves overnight as the flavours settle, so don't be worried about making it ahead. Store it in the fridge without the cream, and stir the cream through when you reheat it gently. It freezes well too on the same basis, no cream until serving.

You'll find it on Burns Night tables across Scotland every January, and it makes a regular appearance at Hogmanay. There's no reason to wait for a special occasion though. This is a midweek soup, something you can have on the table in 45 minutes without any stress.

Ingredients

• 600g undyed smoked haddock fillets (skin on)
• 800ml whole milk
• 150ml cold water
• 1 bay leaf
• 4 black peppercorns
• 40g unsalted butter
• 1 large onion (about 200g), finely diced
• 1 medium leek (about 150g), trimmed and finely sliced
• 700g floury potatoes (such as Maris Piper or Rooster), peeled and cut into 2cm dice
• 75ml double cream, plus a little extra to serve
• Small bunch of chives or flat-leaf parsley, finely chopped, to serve
• Freshly ground black pepper
• Flaky sea salt, to taste (go very carefully)

Method

1. Place the smoked haddock fillets skin-side down in a wide, deep pan. Pour over the milk and cold water, then add the bay leaf and peppercorns. Set over a medium-low heat and bring very slowly to a gentle simmer. You want the surface to just barely tremble, not boil. Cook for 6 to 8 minutes until the haddock is opaque and just cooked through. It should flake easily when pressed with a fork.
   
2. Carefully lift the haddock out onto a plate and leave to cool slightly. Strain the poaching milk through a sieve into a jug and discard the bay leaf and peppercorns. Keep all of the milk, as this is the flavoured base for your soup. Once the fish is cool enough to handle, peel away and discard the skin, then flake the flesh into large pieces, checking carefully for any pin bones as you go. Set the flaked fish aside.
   
3. Melt the butter in a large saucepan over a medium heat. Add the diced onion and sliced leek with a small pinch of salt. Cook gently, stirring regularly, for 10 minutes until both are completely soft and translucent. Don't let them take on any colour.
   
4. Add the diced potatoes to the pan and stir to coat in the buttery onion. Pour over the strained poaching milk, stir everything together, and bring up to a gentle simmer. Cook for 15 to 18 minutes, stirring occasionally, until the potatoes are completely tender.
5. Scoop out roughly half the potato pieces using a slotted spoon and transfer to a bowl. Mash them thoroughly until smooth, then stir the mash back into the soup. This naturally thickens the broth without losing the chunky texture. Leave the remaining potato pieces whole.
   
6. Return the flaked haddock to the pan and stir through gently. Pour in the double cream and stir to combine. Heat over a low heat for 2 to 3 minutes until the fish is warmed through. Taste and season carefully with black pepper and a small amount of flaky salt if needed. The haddock will already have contributed a good deal of saltiness.
   
7. Ladle into warmed bowls. Finish with a small swirl of double cream and a scattering of chopped chives or parsley. Serve straight away with crusty bread and butter, or oatcakes on the side.