Potato Leek Soup

Ingredients

• 28 g (2 tablespoons)unsalted butter
• about 360 g (4 cups), white and light green parts onlychopped leeks
• 1 large clove (about 1 heaped teaspoon), mincedgarlic
• 1 teaspoonkosher salt
• ¼ teaspoon, plus extra for servingground black pepper
• 16 g (2 tablespoons)plain flour
• 900 g (2 pounds), peeled and cut into 2 cm chunksYukon Gold potatoes
• 950 ml (4 cups)low-sodium vegetable stock
• 120–240 ml (½–1 cup), as needed2% or whole milk
• 120 g (½ cup), plus extra for serving; do not use fat-freeplain full-fat Greek yoghurt
• 1 teaspoonwhite wine vinegar
• 1 teaspoonDijon mustard
• ½ teaspoondried dill
• 2 large (about 30 g or ⅓ cup), thinly sliced and dividedspring onions

Instructions

1. 1

   Soften the leeks

   Melt the butter in a large, deep pot or Dutch oven over medium heat. Add the leeks and cook, stirring occasionally, for about 10 minutes until very soft. Adjust the heat so they soften without browning.

2. 2

   Add the flour

   Stir in the garlic, salt and pepper. Sprinkle over the flour and stir vigorously with a wooden spoon for 1 full minute, until no white flour remains.

3. 3

   Pour in stock

   Add the vegetable stock gradually, stirring constantly and pausing between additions to help prevent lumps.

4. 4

   Simmer the potatoes

   Add the potatoes and raise the heat to high. Bring the soup to a steady simmer, cover the pot and turn the heat to low. Simmer for about 25 to 30 minutes, until the potatoes are very soft and starting to fall apart.

5. 5

   Blend until smooth

   Purée the soup with an immersion blender, adding milk as needed to reach your preferred thickness. Alternatively, carefully blend a few ladlefuls at a time in a jug blender, then return each batch to the pot and repeat as needed.

6. 6

   Temper the yoghurt

   Spoon a few portions of hot soup into a medium bowl. Stir in the Greek yoghurt to warm it gradually and help prevent it from curdling.

7. 7

   Stir in yoghurt

   Mix the warmed yoghurt mixture back into the pot of soup.

8. 8

   Finish and serve

   Stir in the vinegar, mustard and dill, then add half of the spring onions. Taste and adjust the seasoning as desired. Serve hot, topped with the remaining spring onions and a few grinds of black pepper.

What is potato leek soup?

Potato leek soup pairs the mild, savoury flavour of leeks with potatoes that soften into a naturally thick base. It is a familiar soup in many home-cooking traditions, and this version takes an American-style approach with vegetable stock, milk and a creamy finish.

Yukon Gold potatoes blend into a smooth, buttery-tasting soup, while dill, Dijon mustard and vinegar add lift. Greek yoghurt gives it a creamy texture without relying only on milk or cream.

Nutrition and macros by portion

The nutrition label shows one serving as written: 238 calories, 8g protein, 42g carbs, 5g fat.

The potatoes provide most of the carbohydrates, while the butter and Greek yoghurt contribute much of the fat; the yoghurt also supplies protein, with smaller amounts from the potatoes and stock. Pair a bowl with a green salad or another serving of vegetables for a more balanced plate.

Choosing and preparing the leeks

Clean leeks: Dirt often collects between the leaves, so rinse them carefully after chopping. Use only the white and light green parts for this recipe.

Sweat gently: Cook the leeks over medium heat until soft, about 10 minutes. Keep them pale rather than browned to preserve their mellow flavour.

Why the flour matters

Coat the vegetables: Stir the flour through the softened leeks for a full minute before adding the stock. This helps disperse it evenly and gives the soup a little extra body.

Add stock gradually: Pour it in slowly while stirring, with brief pauses between additions. That patient approach helps the flour incorporate smoothly instead of forming lumps.

Getting the potatoes tender

Cut evenly: Similar-sized potato chunks cook at roughly the same pace. The recipe calls for pieces about 2 cm across.

Check for doneness: After 25 to 30 minutes of covered simmering, the potatoes should be very soft and beginning to break apart. If they still feel firm when pressed with a spoon, simmer them a little longer.

Blending to the right texture

Use an immersion blender: Blend in the pot until the soup is thick and smooth, then add milk gradually if you prefer a looser consistency.

Use a jug blender carefully: Hot soup can splatter, so blend only a few ladlefuls at a time and take care when handling it. Return each blended batch to the pot before continuing.

Keeping the yoghurt smooth

Temper first: Stir a few spoonfuls of hot soup into the yoghurt before adding it to the pot. Warming it this way helps it mix in more evenly.

Choose full-fat yoghurt: The recipe uses plain whole Greek yoghurt; fat-free yoghurt is more likely to curdle. Sour cream can be used instead.

Finishing and serving

Add brightness: Vinegar, Dijon mustard and dill go in after blending, preserving their fresh, distinct flavours. Stir in just half of the spring onions so some remain crisp for the topping.

Serve it simply: A slice of crusty bread or a green salad makes an easy accompaniment. Finish each bowl with the reserved spring onions and black pepper.

Recipe notes & tips

• Rinse chopped leeks thoroughly to remove grit caught between the layers.
• Keep the leeks pale as they cook; lower the heat if they begin to brown.
• Sprinkle the flour evenly over the leeks and stir until no dry patches remain.
• Add the milk a little at a time after blending so you can control the thickness.
• Temper the yoghurt with hot soup before stirring it into the pot.
• Reserve half of the spring onions for a fresh, crisp garnish.

Variations

• Use sour cream: Swap it for the Greek yoghurt as the recipe allows.
• Change the herbs: Try fresh dill in place of the dried dill, adding it to taste.
• Add extra greens: Serve each bowl with chopped chives or parsley for a fresh garnish.
• Make it chunkier: Blend only part of the soup, then stir it back into the pot.
• Adjust the tang: Add the vinegar gradually and taste before adding the full amount.

Common mistakes to avoid

• Browning the leeks: Keep the heat moderate so they soften gently without taking on colour.
• Adding stock too quickly: Pour it in gradually while stirring to reduce the chance of lumps.
• Stopping before the potatoes soften: Simmer until they are very tender and starting to fall apart.
• Overfilling the blender: Blend hot soup in small batches to help avoid splashes.
• Adding cold yoghurt straight to the pot: Temper it with a few spoonfuls of hot soup first.
• Using fat-free yoghurt: Choose full-fat Greek yoghurt as specified, or use sour cream.

How to store

Refrigerate leftovers in a covered container for up to 3 days. Reheat gently in a saucepan, stirring regularly and avoiding a boil; add a splash of milk or stock if it has thickened.

Frequently asked questions