This simple potato leek soup with dill is perfect to serve on a rainy afternoon alongside a big hunk of crusty sourdough bread. Dill's vibrant, aromatic flavor brings a gorgeous punch of brightness to an otherwise mild, autumn soup.
What is it?
Potato leek soup is rooted in traditional European cookery, and you'll find many variations throughout the continent. In Wales, you'll find cawl cennin while the dish is called soupe aux poireaux or potage parmentier in France. Eastern European recipes for potato soup often call for the addition of fresh dill. In most versions, you simmer leeks and potatoes in broth until tender and then purée them with cream which gives the soup a luxurious, velvety texture. Occasionally, cooks will add fresh herbs, such as chives or parsley, to the soup.
In this version, you'll add chopped fresh dill which brings an element of brightness to the comforting combination of leeks and potatoes.
What's in it?
Potato leek soup typically contains only a handful of ingredients: butter, leeks, potatoes, broth, and cream. This version also contains dill. Since there are so few ingredients, the quality of each one matters as poor-quality broth or lackluster dill can strongly impact the final taste of the soup.
- Butter and salt help to break down the leeks, releasing their flavor. You can also use clarified butter, ghee, or olive oil.
- Leeks are one of the two key ingredients in this soup. They are rich in folate, vitamin K, as well as polyphenols.
- Potatoes give the soup its flavor and body. They are rich in potassium, vitamin C, and vitamin B6. Choose a potato with a medium starch content, such as Yukon Gold, for this soup. Yukon gold potatoes also give this soup a creamy, golden hue.
- Chicken broth gives the soup a savory flavor and a good dose of protein. Choose either bone broth made with chicken bones or chicken broth made from the whole bird. Vegetable stock works in a pinch, but lacks the deeper flavor (and nutrition) of true meat- or bone-based broths.
- Dill has a bright, herbaceous flavor that works well with both potatoes and leeks. Flowering dill offers the most pronounced flavor; however, dill fronds work well, too. Dill is rich in aromatic compounds that give the herb its characteristic flavor. In folk medicine, the herb's traditionally used to ease digestive complaints.
- Cream gives the soup a luxurious finish. Cream from grass-fed cows is rich in vitamin A. It's also a better source of healthy fats, such as omega-3 fatty acids and conjugated linoleic acid, than conventional milk and cream.
Tips for making potato leek soup
This potato leek soup with dill, like most old-world recipes, is simple to make and requires only a few ingredients and very little effort. Despite its simplicity, there are a few things to keep in mind to make sure it comes out every time.
- Rinse the leeks well. Leeks grow in sandy soil and can often retain a bit of sand between their leaves. To slice them, remove the dark green parts and the root tip then, slice them in half lengthwise. Rinse the leeks under water, and then return them to your cutting board. Slice them into half-moons aout ¼-inch thick.
- Sweat the leeks, don't sauté them. Sweating vegetables uses gentle heat and a bit of salt to slowly draw out the flavor of the vegetables without adding color.
- Use a medium-starch potato such as Yukon gold. This gives the soup a good texture without becoming gluey.
- Test the doneness of the potato by pressing it with the tines of a fork. If it breaks apart easily, the soup is ready.
- Skip the upright blender. To purée the soup, use a foodmill or an immersion blender. The high speed of upright blenders can cause the potato's starch to develop, resulting in a glue-like texture. Using a hand-held immersion blender gives you more control, while a food mill processes the soup at a much slower speed.
- Add the dill at the very end. Adding the dill toward the end of cooking and just before puréeing the soup keeps its flavor vibrant and fresh.
- Add the cream at the very end to keep its healthy fats intact. Adding it to early may cause the butterfat to render, creating an oily texture.
Don't have dill fronds? Substitute 1 tablespoon dill seed, ¼ cup fresh dill flowers, or 2 tablespoons dried dill.
Try it with bacon. Skip the butter and fry about 4 ounces of bacon in the Dutch oven. Remove the crisp bacon, and then sweat the leeks in the rendered bacon fat. When the soup is finished, stir in the reserved bacon.
Use parsley instead of dill. Parsley is a lovely match for both potatoes and leeks, and you can swap chopped fresh parsley for the dill.
Add some celeriac. Celeriac (or celery root) is a nice addition. Swap up to ½ pound celeriac for the potatoes in this recipe.
Potato leek soup needs a medium-starch potato, such as Yukon Gold or Yellow Finn. These potatoes have enough starch to break down into a smooth, velvety soup without turning gluey.
To make a dairy-free version, add additional broth in place of cream and substitute olive oil for butter.
We like to serve this soup for lunch alongside toasted sourdough bread and a big green salad.
Alternatively, you can cook ham and add it to the soup as a finishing touch and serve it with a side of fermented vegetables such as sauerkraut. The acidity of fermented vegetables and pickles helps to bring balance to the starchy, creamy nature of the soup.
Yes. You can substitute whole milk or half-and-half for the cream in this recipe, keeping in mind that the soup may taste slightly less rich.
While some recipes call for making a roux from flour and butter, the best way to thicken potato leek soup is to simply purée the potatoes which will thicken the soup naturally. If your soup is still too thin, you can make a slurry of 1 to 2 teaspoons of cornstarch or arrowroot starch and water, and then add it to the soup as it boils.
You'll find versions of Potato Leek Soup in most Northern and Eastern European culinary traditions. There are versions of the soup in Wales, England, France, Ireland, Germany, and Romania among others. They often include the addition of various spices (such as black pepper), herbs (such as parsley and dill), or additional vegetables (such as celeriac).
To store the soup, pour it into a container with a tight-fitting lid, such as a mason jar, and keep it in the fridge for up to 5 days. You may need to add a little broth or water when reheating as potato-based soups thicken in the fridge.
Potato-based soups don't freeze well and may become grainy.