Austrian Lentil Soup with Root Vegetables

Austrian lentil soup, or Linsensuppe, is a hearty Central European-style soup of brown lentils, potatoes, root vegetables, and savory herbs, finished with a little vinegar for brightness. Recipes vary by region and household; this meat-free version builds a rich, satisfying broth with marjoram and vegetables, and it is easy to adapt with sausage or a different root vegetable.

Ingredients

1½ cups (300 g) brown or green lentils, picked over and rinsed
1 tablespoon (15 ml) neutral oil
1 medium yellow onion (about 150 g), finely diced
2 medium carrots (about 160 g total), peeled and diced
1 cup (120 g) diced celery root; or use 2 celery stalks (about 80 g), diced
2 garlic cloves (about 6 g), finely chopped
1 tablespoon (16 g) tomato paste
1 tablespoon (8 g) all-purpose flour
1 teaspoon (1 g) dried marjoram
1 bay leaf
6 cups (1.4 L) low-sodium vegetable broth
2 medium waxy potatoes (about 300 g), peeled if desired and cut into ½-inch (1.25 cm) cubes
1 tablespoon (15 ml) apple cider vinegar, plus more to taste
1 teaspoon (5 g) Dijon or Austrian-style medium mustard
¾ teaspoon (4 g) fine salt, plus more to taste
¼ teaspoon (0.5 g) freshly ground black pepper, plus more to taste
2 tablespoons (8 g) chopped parsley, for serving

Instructions

Prepare the lentils and vegetables. Pick through the lentils for any small stones or damaged pieces, then rinse them under cool running water and drain. Dice the onion, carrots, and celery root into small, similar-sized pieces so they soften evenly. Cut the potatoes into roughly ½-inch cubes and keep them separate; they go into the pot later so they do not turn mushy during the longer lentil simmer.
Soften the vegetables. Warm the oil in a large, heavy soup pot or Dutch oven over medium heat. Add the onion, carrots, and celery root with the salt and pepper. Cook for 6 to 8 minutes, stirring occasionally, until the onion is translucent and the vegetables are beginning to soften. If the bottom of the pot starts to brown too quickly, lower the heat and add a tablespoon of broth.
Build the savory base. Stir in the garlic and tomato paste and cook for about 30 seconds, just until fragrant. Sprinkle the flour over the vegetables and stir for 1 minute to coat them and cook away the raw-flour taste. Add the marjoram and bay leaf. The flour gives the finished soup a gently fuller body rather than making it as thick as a gravy.
Simmer the lentils. Add the rinsed lentils and broth, scraping the bottom of the pot to release any browned bits. Bring the liquid to a boil, then reduce the heat to maintain a steady, gentle simmer. Cover the pot partially and cook for 30 minutes, stirring once or twice. The lentils should be starting to soften but still hold their shape; if the soup boils hard, lower the heat to prevent the lentils from splitting and sticking.
Add the potatoes. Stir in the potato cubes and continue simmering, partially covered, for 15 to 20 minutes. Check a piece of potato and a few lentils: both should be tender, but the potatoes should not have dissolved. Cooking time can vary slightly with the age and variety of lentils, so give them another few minutes if they remain firm. Add a splash of hot water or broth if the soup becomes thicker than you like.
Season and finish. Remove the bay leaf. Stir in the vinegar and mustard, then taste the soup. Add more vinegar a teaspoon at a time if you want a tangier finish, or adjust the salt and pepper. Let it simmer gently for 2 to 3 minutes so the flavors come together. Serve hot with chopped parsley.

Tips

Choose lentils that keep their shape. Brown or green lentils are the best fit here. Red lentils cook much faster and tend to break down into a softer, more puréed soup, so they are not a direct swap; if using them, add them later and check the pot frequently.
Adjust the thickness after simmering. Lentils continue to absorb liquid as the soup stands. Loosen leftovers or a very thick pot with a little hot broth or water, added gradually. If you prefer a thicker bowl, mash a few potatoes and lentils against the side of the pot and stir them back in.
Keep the vinegar for the end. The small amount of acid gives the soup its characteristic lively finish, but adding it early can slow the softening of the lentils. Stir it in once the lentils and potatoes are tender, then taste before adding more.
Make it gluten-free if needed. Leave out the flour; the lentils and potatoes still give the soup body. Check that the broth and mustard are labeled gluten-free, and expect the broth to be slightly less thick.

Serving Suggestions

Serve the soup hot in wide bowls, with parsley and an extra small splash of vinegar at the table for anyone who likes a sharper taste. A slice of dark rye bread, farmhouse-style bread, or crusty sourdough is useful for dipping and makes a simple meal feel complete. For a more substantial spread, add a green salad dressed with a mild vinaigrette or a plate of sliced radishes and cucumbers.

A spoonful of sour cream or crème fraîche is a pleasant optional topping, although it softens the tang of the vinegar. If serving bread alongside the soup, choose something sturdy enough to hold up to the thick lentils. The soup is filling on its own, so a light side is usually a better match than another rich dish.

Variations

Add a smoky sausage garnish: For a heartier, non-vegetarian bowl, serve the soup with cooked smoked sausage sliced into coins. Many smoked sausages are already fully cooked; heat them according to their package directions and serve them in the soup. If using raw ground-pork sausage instead, cook it thoroughly to 160°F (71°C), the USDA FSIS safe minimum for ground meat, checked with a food thermometer. You can brown it in a separate pan and spoon it over the finished soup, or cook it in the pot before the vegetables, draining excess fat as needed. This makes the broth smokier and richer.

Use celery stalks instead of celery root: Celery root, also called celeriac, is a knobby root vegetable with a mild celery flavor and a dense texture. It may be less familiar or harder to find than celery stalks. Stalk celery is a practical substitute and works well in the recipe, though its flavor is lighter and the soup will have a little less earthy sweetness.

Make it more herb-forward: Add a small pinch of dried thyme with the marjoram, or finish with extra parsley. Keep the marjoram prominent if you want the soup to retain its Austrian-inspired character; too much thyme can take the flavor in a different direction.

Use smoked paprika for a meat-free smoky note: Stir ¼ teaspoon (about 0.5 g) smoked paprika into the tomato paste, then taste before adding more. It is not a traditional replacement for sausage, but it adds gentle smoke without meat. Avoid using a large amount, which can overwhelm the mild lentils and root vegetables.

Storage and Reheating

Cool the soup promptly and refrigerate it within 2 hours of cooking in shallow, covered containers. It keeps for 3 to 4 days in the refrigerator. The lentils will absorb some broth as they sit, so add a little water or broth before reheating if the texture has become very thick.

Reheat only the portion you plan to serve in a saucepan over medium-low heat, stirring occasionally until steaming hot throughout. If checking with a food thermometer, leftovers should reach 165°F (74°C). You can also reheat an individual portion in the microwave, stirring partway through and checking that it is hot throughout. Avoid repeatedly cooling and reheating the full pot.

For longer storage, freeze the cooled soup in freezer-safe containers, leaving a little space for expansion. It freezes well for up to 3 months for best quality. Thaw it overnight in the refrigerator or reheat it from frozen over low heat, adding a splash of broth or water as needed. Potatoes can become slightly softer after freezing, but the soup remains flavorful.

Frequently Asked Questions

Do I need to soak the lentils?
No. Brown and green lentils cook in the time given without soaking. Rinse them and check for small stones or debris before they go into the pot. If you happen to soak them, they will cook more quickly, so begin checking well before the listed simmer time is up.

Can I make Austrian lentil soup without celery root?
Yes. Use diced celery stalks as listed, or use a little extra carrot if neither is available. Celery root gives the broth a rounder, earthier flavor, while celery stalks taste fresher and lighter. Keep the cut pieces small so they soften along with the onion and carrots.

Why are my lentils still firm?
Lentils vary in age and can take longer to soften, especially if they have been stored for a long time. Continue simmering gently and check them every 5 minutes. Make sure they stay covered with liquid, adding hot broth or water if needed. Avoid adding the vinegar until they are tender, since acidic ingredients can slow softening.

Can I make the soup ahead?
Yes. The flavors settle in nicely after a night in the refrigerator, and the soup is convenient to prepare ahead for a meal. It will thicken as it rests, so stir in broth or water while reheating. Keep it refrigerated and use it within 3 to 4 days, or freeze portions for up to 3 months for best quality.

How can I make the soup vegetarian or vegan?
The recipe as written is vegetarian and vegan when you use vegetable broth and a plant-based mustard. Check ingredient labels, since broths and condiments vary. If you serve it with sour cream or sausage as an optional topping, those additions are not vegan; parsley, bread, or a plant-based topping keep the bowl meat-free.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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