Cheesy leek and potato soup

Leeks and potatoes make a soft, hearty soup finished with melting cheddar.

This recipe makes 4 servings and takes about 15 minutes to prepare plus 30 minutes to cook. Metric and imperial quantities are alternate measurements, so use one system rather than adding both. If you change the yield, keep the pan size and thickness of the food in mind: a crowded pan steams food and a deep baking dish can extend the cooking time.

Equipment

Set out large saucepan with lid, wooden spoon, stick blender, ladle. A wide pan gives moisture somewhere to evaporate; for an oven dish, leave space between pieces so heat can circulate. Use separate board and knife surfaces for raw protein and foods that will be eaten without further cooking.

Ingredients

You will need: leeks, sliced and washed: 400 g (14 oz); floury potatoes, diced: 500 g (1 lb 2 oz); butter: 25 g (1¾ tbsp); vegetable stock: 1 litre (4¼ cups); fresh thyme leaves: 5 g (1 tbsp); Dijon mustard: 10 g (2 tsp); mature cheddar, grated: 150 g (5 oz); chives, chopped: 10 g (⅓ oz). Gather the ingredients before heating the pan so the aromatics do not burn while a measurement is being found.

• leeks, sliced and washed — 400 g / 14 oz
• floury potatoes, diced — 500 g / 1 lb 2 oz
• butter — 25 g / 1¾ tbsp
• vegetable stock — 1 litre / 4¼ cups
• fresh thyme leaves — 5 g / 1 tbsp
• Dijon mustard — 10 g / 2 tsp
• mature cheddar, grated — 150 g / 5 oz
• chives, chopped — 10 g / ⅓ oz

Method

Read the full method once, then prepare the ingredients in the order listed. Keep raw and ready-to-eat ingredients separate, and wash hands and equipment after raw-protein contact.

Step 1

Melt butter in a saucepan and cook leeks for 8 minutes until soft but not coloured.

Step 2

Add floury potatoes, vegetable stock and thyme. Cover and simmer for 18 minutes, until the potatoes break easily when pressed.

Step 3

Blend the soup partly for a thick texture, then stir in Dijon mustard and mature cheddar until melted.

Step 4

Ladle into bowls, scatter with chives and serve steaming hot.

Cooking and safety check

Simmer until potatoes are completely tender and reheat the finished soup until steaming. A time estimate and a browned surface do not prove that the centre is cooked. Use a suitable food thermometer where the ingredient or local guidance requires one, and follow the package or official instructions for the specific food.

Substitutions that respect the dish

A substitution should preserve the recipe’s job, not merely its colour. Use olive oil for butter for a dairy-free base. Use a dairy-free cheddar alternative; it may melt differently and should be checked for allergens. Use wholegrain mustard instead of Dijon mustard; both are mustard allergens.

• Use olive oil for butter for a dairy-free base.
• Use a dairy-free cheddar alternative; it may melt differently and should be checked for allergens.
• Use wholegrain mustard instead of Dijon mustard; both are mustard allergens.

Allergen notes

This recipe contains or may contain milk, mustard, celery may be present in packaged stock. Check every packaged ingredient because formulations and cross-contact warnings vary.

Common mistakes and how to correct them

Use one troubleshooting change at a time. If the centre is undercooked, return it to the appropriate heat and check again rather than relying on the outside colour. If the pan is dry, add liquid gradually; if it is watery, reduce uncovered. Texture may also reflect crowded equipment, a different ingredient size, or a changed batch quantity.

• Wash leeks between layers to remove grit.
• Blend only half the soup if you prefer visible potato pieces.
• Add cheddar off the boil to keep the soup smooth.

Leftovers and storage

Cool quickly, refrigerate for up to three days, and reheat on the hob until steaming. Freeze without chives for up to one month.

Serving ideas

These sides and finishes suit cheesy leek and potato soup without changing the recipe itself.

• Warm baguette
• Pear and walnut salad
• Roasted cherry tomatoes

Frequently asked questions

Can I leave the soup unblended?

Yes; dice the potatoes small so they are spoon-tender.

Why did my cheese become grainy?

The soup was probably boiling; melt cheddar over low heat.

Related recipes and tools

Browse the related recipes for a different appliance, pace, or ingredient pairing. Use the serving scaler only after checking the stated yield, and use the storage guide before deciding whether to save a portion. Related links help with the next decision; they do not make this recipe suitable for every diet or kitchen.