Scottish Recipes UK: Cullen Skink Soup

Cullen skink is a Scottish soup associated with the coastal town of Cullen in Moray, made with smoked haddock, potatoes, onion and milk. This creamy, filling version keeps the fish in generous flakes and the potatoes partly broken down, so the broth is rich without needing a thickener; family and regional versions vary in how much cream or potato they use.

Ingredients

1 lb (450 g) skinless, boneless smoked haddock, preferably undyed
1 tablespoon (14 g) unsalted butter
1 medium yellow onion, finely diced, about 1 cup (150 g)
1¼ lb (570 g) floury potatoes, such as Maris Piper or russets, peeled and cut into ½-inch (1.25 cm) cubes
3 cups (720 ml) whole milk
1 cup (240 ml) water
1 bay leaf, about 0.2 g
½ teaspoon (3 g) fine salt, plus more only if needed
¼ teaspoon (0.5 g) freshly ground black pepper, plus more to taste
½ cup (120 ml) heavy cream
2 tablespoons (8 g) chopped fresh parsley, for serving

Instructions

Prepare the ingredients. Dice the onion, peel and cube the potatoes, and check the haddock for any remaining pin bones. Cut the fish into two or three large pieces if needed so they sit comfortably in your saucepan. Keep the fish chilled while you start the soup. Allow about 20 minutes for this preparation, including peeling and chopping.
Soften the onion. Melt the butter in a large, heavy saucepan over medium-low heat. Add the diced onion and cook for 8 minutes, stirring every minute or two. It should become soft and translucent but not brown; turn the heat down if the edges begin to colour. A gentle start keeps the soup sweet and mild rather than giving it a fried-onion flavour.
Cook the potatoes in the milk. Add the potato cubes, milk, water, bay leaf, salt and pepper. Raise the heat just until the liquid begins to steam and show small bubbles around the edge, then turn it down to maintain a gentle simmer. Cook uncovered for 15 minutes, stirring carefully once or twice so the potatoes cook evenly and do not catch on the bottom. Avoid a hard boil, which can cause milk to scorch or foam over.
Poach the haddock. Lower the fish pieces into the simmering liquid and cook gently for about 8 minutes, turning once if they are not fully submerged. Check the thickest piece with a food thermometer: fish should reach the USDA FSIS safe minimum internal temperature of 145°F (63°C). The flesh should look opaque and separate easily into flakes. Lift the cooked fish onto a plate with a slotted spoon and remove the bay leaf from the pan.
Flake the fish and finish the soup. When cool enough to handle, break the haddock into large flakes, checking again for pin bones. This takes about 2 minutes. Return the fish to the pan and gently stir in the cream. Simmer for 4 minutes without letting the soup boil. Taste a spoonful before adding extra salt, since smoked haddock can be quite salty. For a thicker texture, press a few potato cubes against the side of the pan and stir them into the broth; leave the other pieces intact.
Serve. Ladle the soup into warmed bowls and scatter over the parsley and a little extra black pepper. Keep the fish in visible flakes when serving rather than stirring vigorously, which can break it up and make the soup less attractive.

Tips

Choose haddock with care. Undyed smoked haddock gives the soup a natural, pale colour and a rounded smoky taste. Finnan haddie is a traditional Scottish-style smoked haddock, but it may be difficult to find outside the UK. If it is unavailable, use smoked cod or another mild smoked white fish; the soup will still work, though its flavour and texture may be a little different. If using a strongly smoked or heavily salted fish, taste before seasoning.
Keep the heat gentle. Milk can scorch at the base of the pan and may boil over, especially once potatoes release starch. Use a heavy-based saucepan, stir the bottom regularly, and lower the heat as soon as the liquid starts simmering. If the milk looks as though it is about to boil, briefly move the pan off the burner.
Pick a potato that softens well. Floury potatoes help thicken the broth as some edges break down. Waxy potatoes hold their shape more firmly, which is also pleasant but makes a thinner soup. If using waxy potatoes, mash a few cubes at the end to give the liquid more body rather than adding flour.
Adjust richness at the end. The cream is optional if you prefer a lighter soup: replace it with the same amount of whole milk. For a richer bowl, keep the cream, but do not add it while the fish is still cooking or boil the finished soup hard. Either can make the fish break apart and the dairy taste less fresh.

Serving Suggestions

Serve Cullen skink hot as a substantial starter or as the main course for lunch or a simple supper. Warm, crusty bread is a natural accompaniment for dipping into the smoky milk broth; oatcakes or plain crackers offer a crisp contrast without competing with the fish. A small green salad dressed with a mild vinaigrette can balance the soup’s creaminess if you are serving it as a full meal.

For a traditional Scottish-inspired table, offer oatcakes and butter alongside the bowls, and put extra parsley and black pepper on the table so everyone can finish their own serving. The soup is filling, so modest portions work well before a larger meal. If serving guests, warm the bowls first and ladle the soup just before eating; it cools quickly because of its milk base.

Variations

Many versions use only milk, while others include cream or more potato. For a more rustic bowl, use 1½ lb (680 g) potatoes and omit the cream, adding a splash of milk if the soup becomes too thick. For a smoother texture, mash roughly one-third of the cooked potatoes before adding the flaked fish. Avoid blending the entire pot after adding the haddock, as that turns the fish into fine shreds and changes the characteristic texture.

You can replace the onion with one small leek, about 1 cup (100 g) finely sliced, for a gentler, slightly sweeter flavour. Cook it in the butter in the same way, checking that it is tender before adding the potatoes. For a stronger smoky note, use a mix of 12 oz (340 g) smoked haddock and 4 oz (115 g) unsmoked haddock, or use all smoked fish for the full savoury flavour. Do not add extra salt until you have tasted the finished broth.

For a dairy-free adaptation, cook the onion in olive oil or a dairy-free spread and use an unsweetened, unflavoured oat drink in place of the milk, with a little extra water as needed. Add the oat drink over low heat and avoid boiling it, since some brands separate when simmered. The result will not have the same classic milky richness, but the potatoes and smoked fish still make a satisfying soup. Check that the smoked fish is suitable for the diners’ dietary needs, as products can vary in ingredients and salt content.

Storage and Reheating

Cool leftovers promptly and refrigerate them within 2 hours of cooking in a covered, shallow container. Keep the soup refrigerated for 3–4 days. Because it contains fish and dairy, do not leave it sitting at room temperature for an extended period, and do not rely on smell alone to decide whether old leftovers are safe. For longer storage, freeze portions in airtight freezer-safe containers for up to 2 months for best quality. The potatoes may become softer after freezing, and the dairy can separate slightly, but gentle reheating and stirring usually bring the soup back together.

Reheat only the portion you need in a saucepan over low to medium-low heat, stirring often and bringing it to 165°F (74°C), the USDA FSIS safe temperature for reheated leftovers. Do not let it boil vigorously. If it has thickened in the fridge, loosen it with a small splash of milk or water while it warms. Microwave reheating is also possible: use a microwave-safe bowl, cover loosely, heat in short intervals, and stir between intervals so the centre heats evenly to 165°F (74°C). Once reheated, do not cool and reheat the same portion repeatedly.

Frequently Asked Questions

What is Cullen skink?
Cullen skink is a Scottish smoked-haddock soup traditionally associated with Cullen, a town on the Moray coast. Potatoes and onion make it hearty, while milk or cream forms the broth. Recipes vary from household to household, especially in how thick and creamy the finished soup should be.

Can I make Cullen skink with fresh haddock?
Yes, but the soup will lack the distinctive smoky taste that defines this style of Cullen skink. If you use fresh haddock, season carefully and consider adding a small amount of smoked fish rather than trying to imitate the flavour with extra salt. Cook the fish to 145°F (63°C), checked with a food thermometer.

Can I use frozen smoked haddock?
Thaw it safely in the refrigerator before cooking, then pat it dry and check for bones. If cooking from frozen, the fish will release more water and take longer to heat through, so the recipe timing will change. The reliable check is the thickest part reaching 145°F (63°C), not a fixed number of minutes.

Why has my soup turned out thin?
Potato variety and how small the cubes are affect how much starch enters the broth. Simmer the soup gently for a few extra minutes before adding the fish, or mash a few potato pieces into the liquid. Do not thicken it with a large amount of flour, which can make the broth taste pasty.

Can I make it ahead?
You can prepare the onion and potatoes ahead and refrigerate them separately, but the soup is best when the haddock is gently cooked close to serving time. If you make the complete soup in advance, cool and refrigerate it promptly, then reheat it slowly to 165°F (74°C). The fish may flake more after reheating, so stir gently.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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