Roasted Sweet Potato and Leek Soup

Ingredients

• 907 g (2 pounds), peeled and cut into 5 cm (2-inch) chunkssweet potatoes
• 52.5 ml (3½ tablespoons), dividedextra virgin olive oil
• 28 g (2 tablespoons)unsalted butter
• 1 large, cleaned and thinly slicedleek
• 1 large, dicedshallot
• 2 cloves, mincedgarlic
• 15 ml (1 tablespoon), mincedfresh thyme
• 10 ml (2 teaspoons), mincedfresh sage
• A pinchfresh nutmeg
• 590–830 ml (2½–3½ cups), warmchicken or vegetable stock
• To tastesalt and pepper
• To tastesour cream
• To tastecandied pecan pieces
• To tastediced pancetta

Instructions

1. 1

   Heat the oven

   Preheat the oven to 190°C (375°F).

2. 2

   Season the potatoes

   Arrange the sweet potato chunks on a large baking tray. Drizzle with 37.5 ml (2½ tablespoons) of the oil, season with salt and pepper, and toss to coat.

3. 3

   Roast until tender

   Roast the potatoes for 35–40 minutes, tossing them halfway through, until they are tender when pierced with a fork.

4. 4

   Set potatoes aside

   Take the tray out of the oven and set the roasted potatoes aside.

5. 5

   Warm the fats

   Set a large saucepan over a medium heat and add the remaining oil and the butter.

6. 6

   Soften the vegetables

   Add the leek, shallot and garlic. Sauté for 4–5 minutes, until the leek and shallot are slightly translucent, then season with salt and pepper.

7. 7

   Add the herbs

   Stir in the thyme and sage and sauté for a further 3–4 minutes.

8. 8

   Blend the soup

   Put the roasted potatoes and leek mixture into a blender and add 590 ml (2½ cups) of warm stock. Blend until smooth and thick enough to coat the back of a spoon, adding more stock as needed.

9. 9

   Simmer gently

   Pour the puréed soup back into the saucepan and season with salt and pepper. Simmer for 4–5 minutes.

10. 10

    Finish and serve

    Stir in a pinch of nutmeg. Serve with sour cream, diced pancetta and candied pecan pieces, if using.

What is roasted sweet potato and leek soup?

This is a blended vegetable soup built around sweet potatoes and leeks, finished with herbs and a little nutmeg. Roasting the potatoes before they meet the saucepan gives them a more concentrated, gently caramelised flavour.

Leek and potato soups are a familiar pairing in British and European home cooking, though this version centres sweet potato rather than the usual white potato. Sour cream, pancetta and candied pecans offer optional creamy, savoury and sweet contrasts.

Nutrition and macros by portion

The nutrition label shows one serving as written: 220 calories, 4g protein, 29g carbs, 11g fat.

Sweet potatoes supply most of the carbohydrate, while olive oil and butter contribute much of the fat; the vegetables and stock provide only a modest amount of protein. Pancetta and sour cream will add further fat and protein, so pair a bowl with salad or other vegetables for a more balanced plate.

Roast the sweet potatoes well

Even chunks: Cut the potatoes into pieces of roughly the same size so they become tender at about the same time. A large baking tray gives them room to roast rather than steam.

Tenderness: Toss the pieces halfway through the 35–40 minutes. They are ready when a fork slides into the centre easily.

Build the leek and herb base

Gentle heat: Sauté the leek, shallot and garlic in the oil and butter until the leek and shallot are slightly translucent. Keep the heat moderate so the garlic softens without browning.

Herbs: Adding the thyme and sage after the vegetables have softened gives them a few minutes in the pan to release their fragrance before blending.

Blend to the right texture

Start with less stock: Blend the roasted potatoes and sautéed vegetables with 590 ml of warm stock first. The recipe aims for a smooth soup thick enough to coat the back of a spoon.

Adjust gradually: Add more stock a little at a time if the soup is too thick. The full amount depends on the potatoes and how loose you like your soup.

Check the finish

Smoothness: Blend until no noticeable pieces of potato or leek remain. If your blender is small, blend in batches and take care when handling hot ingredients.

Seasoning: Taste after simmering, then adjust the salt and pepper. Add the nutmeg at the end so its warm aroma remains noticeable without dominating the herbs.

Choose your toppings

Creamy: A spoonful of sour cream adds a cool, tangy contrast to the sweet, warm soup. Swirl it in just before serving.

Crunchy and savoury: Candied pecans bring a sweet crunch, while pancetta adds a salty, savoury note. Both are optional, so you can use one, both or neither.

Make it a meal

Serve the soup with crusty bread or toast for dipping. A simple green salad alongside can add freshness and contrast to the rich, smooth texture.

For a more substantial bowl, use the pancetta topping and serve with bread. For a lighter-feeling plate, keep the toppings modest and add a generous salad.

Recipe notes & tips

• Cut the sweet potatoes into evenly sized chunks so they roast at a similar pace.
• Use a large baking tray and spread the potatoes out to help them roast rather than steam.
• Warm the stock before blending to keep the soup hot and make it easier to adjust the texture.
• Add stock in small amounts after the initial blend, stopping when the soup coats a spoon.
• Blend in batches if needed, and follow your blender’s instructions for hot liquids.
• Taste the soup after simmering, as the stock and toppings can vary in saltiness.

Variations

• Vegetable stock: Use vegetable stock to make the soup without chicken stock.
• No pancetta: Leave it out for a meat-free bowl.
• Extra sage: Add a little more minced sage for a stronger herbal note.
• Chunkier texture: Blend only part of the soup, then stir it back into the pan.
• Toasted pecans: Use plain toasted pecans instead of candied ones for a less sweet crunch.

Common mistakes to avoid

• Crowded tray: The potatoes may steam instead of roast; spread them out across a large tray.
• Uneven chunks: Pieces may cook at different rates; cut them to roughly the same size.
• Browning garlic: It can turn bitter; keep the pan at medium heat and sauté only until the vegetables soften.
• Too much stock at once: The soup can become thinner than intended; begin with 590 ml and add more gradually.
• Skipping the halfway toss: The potatoes may roast unevenly; turn them once during the cooking time.
• Over-seasoning early: Stock and toppings can be salty; taste the finished soup before adding more salt.

How to store

Refrigerate leftover soup in a covered container for up to 3 days. Reheat gently in a saucepan, stirring and adding a splash of stock or water if it has thickened; store toppings separately and add them when serving.

Frequently asked questions