Potato Leek Soup
Potato leek soup is the first thing I make when the weather turns. It’s one pot, about 45 minutes, and the ingredient list is short enough that you probably have most of it already.
The soup itself is humble — leeks, onion, potatoes, stock. What makes it worth posting is the finish: a swirl of cream, fresh parsley, croutons, and crispy pancetta crumbled over the top.
INGREDIENTS NEEDED:
Leeks — 2 medium (~300 g / 10 oz). White and light green parts only; the dark green tops are too tough, but don’t throw them out, they’re great for stock. Leeks trap sand between their layers, so halve them lengthwise and rinse properly.
Onion — 1 medium, diced. Sounds redundant next to the leeks, but it adds a rounder sweetness that leeks alone don’t have.
Garlic — 2 cloves, minced. In late and only for a minute, so it perfumes the soup instead of turning bitter.
Potatoes — 3 medium (~500 g / 1 lb), peeled and cubed. Floury potatoes blend the creamiest. Waxy ones work but stay a little denser. Cube them evenly so they cook at the same rate.
Pancetta — 6–8 thin slices (~90 g / 3 oz). Crisped and crumbled over the top. Diced bacon works too, it just renders more fat, so drop the butter a little.
Butter — 2–3 tbsp. This is what the leeks sweat in, together with the pancetta fat. Don’t skip it and don’t skimp.
Stock — 450–600 ml (2–2½ cups). Vegetable, chicken or beef, whatever you have. Start with less than you think; you can always thin the soup after blending, but you can’t un-thin it.
Dried thyme — ¼ tsp. Quiet, earthy, exactly right here. Rosemary works too if that’s what’s in the cupboard.
Bay leaf — 1. Goes in with the stock and comes out before blending. A blended bay leaf turns the whole pot bitter and gritty.
Heavy cream — 75 ml (⅓ cup), plus extra for swirling on top. Stirred in after blending, off the heat.
Salt and black pepper — more salt than feels right. Potatoes absorb an enormous amount.
To serve — parsley, croutons, extra cream, and the reserved pancetta.
HOW TO MAKE POTATO LEEK SOUP:
1. Crisp the pancetta. Lay the slices in a dry pot over medium heat, or spread them on a lined tray and bake at 200°C / 400°F for 10–12 minutes. Either way you want them properly crisp, not chewy. Move them to paper towel, let them cool for a minute, then crumble into shards. Leave every drop of rendered fat in the pot, that’s seasoning for the whole soup.
2. Sweat the leeks and onion. Add the butter to the pancetta fat and let it foam, then tip in the sliced leeks and diced onion. Turn the heat down and cook 8–10 minutes, stirring now and then. You’re after completely soft and translucent with no color at all.
3. Add the garlic. One minute, stirring constantly, just until you can smell it. Any longer over this kind of heat and it goes bitter.
4. Season the base. Salt, black pepper and the thyme go in now, not at the end. Seasoning the aromatics while they’re soft builds flavor into the base instead of sitting on top of it.
5. Add the potatoes. Tip in the cubes and stir for a minute so they’re coated in the buttery leeks.
6. Stock and bay leaf. Pour in just enough stock to cover the potatoes — around 450 ml, but go by the pot, not the number. Drop in the bay leaf, bring to a gentle simmer, cover and cook 15–20 minutes. They’re done when a cube falls apart against the side of the pot with no resistance. Don’t be tempted to simmer it for 40 minutes; it won’t get creamier, it’ll just lose the leek flavor.
7. Remove the bay leaf and blend. Fish the bay leaf out first. Then blend with an immersion blender in short pulses, moving it around the pot. Stop the moment it’s smooth. Potato starch turns gluey when it’s overworked, which is why a high-speed countertop blender is the wrong tool here. If you don’t have an immersion blender, mash it roughly instead; the rustic version is genuinely good.
8. Cream, taste. Stir the cream in off the heat. Check the thickness and loosen with a splash more stock if it’s too dense. Now taste it, and taste it properly.
9. Serve. Ladle into bowls, swirl a little cream over the surface, then pile on the parsley, croutons and crumbled pancetta. Eat straight away while the pancetta is still crisp.
TIPS:
- Start with less stock than you think. Thinning is easy, thickening isn’t.
- Salt in layers — once with the leeks, once at the end.
- Crisp the pancetta fresh each time. It goes soft in the fridge.
How to Store Potato Leek Soup:
Fridge: Keep the soup in an airtight container for up to 4 days. Store the toppings separately: pancetta and croutons go soft overnight, and parsley wilts.
Freezer: Potato soups can turn slightly grainy once frozen, and cream can split. For the best texture, freeze the soup after blending but before adding the cream, for up to 3 months. Thaw overnight in the fridge, then stir in the cream while reheating.
Reheating: Warm it gently over medium-low heat and stir often. Don’t let it boil once the cream is in. The soup thickens as it sits, so loosen it with a splash of stock or water. If the texture looks a little grainy after freezing, whisk hard or give it a few quick pulses with the immersion blender.
Make ahead: Make the soup a day ahead (it tastes even better the next day). Crisp the pancetta fresh just before serving.
Potato and Leek Soup
Ingredients
Method
- Crisp the pancetta in a dry pot over medium heat (or bake at 200°C / 400°F for 10–12 minutes). Drain on paper towel, then crumble. Leave the rendered fat in the pot.
- Add the butter to the pancetta fat. Once it foams, add the leeks and onion. Lower the heat and cook for 8–10 minutes, until soft and translucent but not browned.
- Add the garlic and stir for 1 minute, until fragrant.
- Season with salt, black pepper and thyme.
- Add the potatoes and stir for 1 minute to coat.
- Pour in just enough stock to cover the potatoes (about 450 ml). Add the bay leaf, bring to a gentle simmer, then cover and cook for 15–20 minutes, until the potatoes fall apart easily.
- Remove the bay leaf. Blend with an immersion blender in short pulses until just smooth. Don't overblend, or the soup will turn gluey.
- Take the pot off the heat and stir in the cream. Thin with extra stock if needed. Season generously with salt, then add the lemon juice.
- Ladle into bowls. Top with a swirl of cream, parsley, croutons and crumbled pancetta. Serve immediately.
Notes
- Stock: Start with less than you think. Thinning is easy, thickening isn’t.
- Salt in layers: once with the leeks and again at the end. Potatoes absorb a lot of salt.
- Bacon instead of pancetta: Diced bacon works, but it renders more fat, so use less butter.
- No immersion blender? Mash it roughly for a rustic version. Avoid high-speed countertop blenders, which make potato soup gluey.
- Leek tops: Save the dark green tops for homemade stock.
- Storage: Refrigerate for up to 4 days with the toppings stored separately. Freeze before adding the cream for up to 3 months.