Cullen Skink (Haddock and Potato Soup)

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Introduction

Cullen Skink is a Scottish smoked fish and potato soup that relies on the clean, assertive flavor of smoked haddock to carry the entire dish—no cream, no stock cubes, just fish, potatoes, and milk built into a thick, warming bowl. The soup takes about 40 minutes total and works equally well as a light lunch or a first course before a heavier main.

Recipe Details

• Prep Time: 10 minutes
• Cook Time: 30 minutes
• Total Time: 40 minutes
• Servings: 4

Ingredients

• 1 large (2 lb) smoked haddock, preferably Finny haddock
• 1 medium onion, finely chopped
• 1½ pints milk
• 2 tablespoons butter
• 8 oz mashed potato
• Salt
• Pepper
• 1 bay leaf
• Parsley, chopped
• Water
• Toast (optional)

Instructions

1. Cover the haddock with water in a shallow pan with skin side down.
2. Bring to the boil and simmer for 5 minutes, turning once.
3. Take the fish from the pan and remove the skin and bones.
4. Flake the fish and return to the stock.
5. Add chopped onion, bay leaf, salt and pepper.
6. Simmer for a further 10 minutes.
7. Strain the stock and keep it ready. Discard the bay leaf and keep the fish warm.
8. Add the milk to the fish stock and bring to the boil.
9. Add mashed potato to make a rich and thick soup.
10. Add the fish and check the seasoning-add more if needed.
11. When serving, add the butter in small pieces so it runs through the soup.
12. Serve with chopped parsley on top, and toast by the side.

Variations

Use fresh haddock instead of smoked. You’ll lose the signature smokiness, but the soup still works; add a pinch of smoked paprika to the final bowl if you want to recover some of that depth.

Swap the mashed potato for floury potatoes cut into small cubes. The soup will be brothier and less creamy, with more distinct potato texture; add them in step 5 and simmer until tender rather than stirring in mash at the end.

Replace half the milk with fish or vegetable broth. This lightens the richness and sharpens the fish flavor, making the soup less heavy for summer eating or lighter appetites.

Add diced carrot or celery to the onion. Chop them finely and simmer them together in steps 5–6; they add subtle sweetness and vegetable body without overwhelming the haddock.

Finish with a squeeze of fresh lemon juice instead of—or alongside—the butter. A small acidic note brightens the smoked fish and balances the starch; add it just before serving.

Tips for Success

Use proper smoked haddock, not smoked cod. Haddock has a milder, sweeter smoke flavor that suits the delicate soup structure; smoked cod is stronger and can overpower the milk and potato balance.

Don’t skip the initial 5-minute poach of the whole fish. This step extracts flavor into the cooking water and firms the flesh so it flakes cleanly without turning to mush; turning it halfway ensures even cooking.

Strain the stock before adding the milk. Small bones and skin fragments left behind will cloud the finished soup and create gritty texture; take the 30 seconds to pour through a fine sieve.

Stir the mashed potato in gradually, not all at once. If you dump it in, you risk lumps; whisk or stir gently as you add it, and the soup will thicken evenly and stay smooth.

Add the butter at the table, not during cooking. Heating it with the soup will break the emulsion and make the fat separate; add small pieces just before eating so they melt into the hot soup.

Storage and Reheating

Store in an airtight container in the fridge for up to 3 days. The soup thickens further as it cools, so thin it with a splash of milk or broth when reheating.

FAQ

Can I make this soup ahead and reheat it?

Yes, but only up to 3 days in the fridge. The soup thickens as it sits, so add a little extra milk or broth when you reheat it on the stovetop to bring it back to the right consistency.

What if I can’t find smoked haddock?

Use smoked cod or smoked mackerel, but reduce the quantity slightly—both are stronger-flavored fish. Alternatively, use fresh haddock and add a pinch of smoked paprika to mimic the smoky depth.

Why does my soup look curdled or grainy after reheating?

Can I use instant mashed potato or leftover mash from another meal?

Yes to both. Instant potato works fine—use the package amount for 8 oz of mash. Leftover mash is even better, as it’s already cooked and won’t introduce lumps if you stir it in carefully.