Irish Seaweed Soup with Dulse and Potatoes

Irish seaweed soup is a coastal-style soup made with dulse, potatoes, leeks, and a gently creamy broth. Dulse brings a savory, briny note while the potatoes make the soup hearty; recipes vary by cook, and this version keeps the flavors simple and balanced.

Ingredients

1/2 cup (15 g) loosely packed dried dulse flakes, or finely snipped dried dulse leaves
2 tablespoons (28 g) unsalted butter
1 medium yellow onion, finely diced, about 1 cup (150 g)
2 medium leeks, white and light-green parts only, sliced and well rinsed, about 2 cups (200 g)
1/2 cup (60 g) diced celery, about 1 small stalk
1 pound (450 g) waxy or all-purpose potatoes, peeled if desired and cut into 1/2-inch (1.3 cm) cubes
5 cups (1.2 L) low-sodium vegetable stock or chicken stock
1 teaspoon (5 ml) Dijon mustard
1 cup (240 ml) whole milk
1/2 cup (120 ml) heavy cream
1/4 teaspoon (1.5 g) fine salt, plus more only if needed
1/4 teaspoon freshly ground black pepper
1 tablespoon (15 ml) fresh lemon juice
2 tablespoons (8 g) chopped fresh parsley, for serving

Instructions

Prepare the seaweed and vegetables. Check the dulse for any grit or hard stems. If it looks sandy, rinse it briefly in a fine-mesh strainer under cool water, drain well, and chop or crumble it into small pieces. Slice the leeks, then rinse them thoroughly in a bowl of water, separating the layers so trapped soil falls to the bottom. Lift the leeks out rather than pouring the water over them. Dice the onion, celery, and potatoes.
Soften the aromatics, 8 minutes. Melt the butter in a large, heavy pot over medium heat. Add the onion, leeks, and celery. Cook for about 8 minutes, stirring every minute or two, until the vegetables are soft and fragrant but not browned. If the leeks begin to stick, lower the heat and add a spoonful of stock.
Add the potatoes, stock, and dulse, 2 minutes. Stir in the potatoes and Dijon mustard, then pour in the stock. Add the dulse and black pepper. Bring the liquid just to a boil, stirring once to distribute the seaweed, then reduce the heat so the soup simmers gently.
Simmer until the potatoes are tender, about 20 minutes. Partially cover the pot and cook, stirring occasionally, until a knife slides easily into a potato cube. Keep the simmer gentle; a hard boil can break up the potatoes and make the broth cloudy. Dulse can vary in saltiness, so wait until the end to decide whether additional salt is needed.
Make the broth creamy, about 5 minutes. Stir in the milk and cream and warm the soup over low heat for about 5 minutes, without letting it boil. Taste, then add the measured salt if needed and the lemon juice. The lemon should brighten the broth rather than make it taste sour. For a thicker texture, mash a few potato cubes against the side of the pot and stir them back in; leave the rest whole for a satisfying chunky soup.
Finish and serve. Ladle into warm bowls and scatter parsley over the top. Taste one last spoonful before serving: a little black pepper or a few drops of lemon can sharpen the flavors, while extra salt is rarely needed if the dulse or stock is already salty.

Tips

Choose food-grade dulse. Look for dried dulse sold for cooking, with a clean, sea-like smell and no visible grit. Dulse is a red seaweed gathered along North Atlantic coasts, including Ireland, but products differ in cut, color, and saltiness. If you use whole leaves, crumble or chop them so they soften evenly and are easy to eat.
Adjust for fresh dulse. Fresh dulse can replace dried, but it contains more water and its flavor may be less concentrated. Use roughly 1 cup (30 g) chopped fresh dulse as a starting point, rinse it carefully, and taste before adding salt. The soup will have a softer seaweed flavor than a batch made with dried flakes.
Keep the heat gentle after adding dairy. Milk and cream can separate if the soup boils vigorously. Warm them slowly over low heat and serve once the soup is steaming. If you need to hold the soup briefly, keep it on the lowest setting and stir occasionally rather than allowing it to bubble.
Let the dulse guide the seasoning. Stock and seaweed both bring salt, so use low-sodium stock and season near the end. If the finished soup tastes too salty, add a little hot water or unsalted stock and a few extra cooked potato cubes; adding more cream alone can soften the flavor but will not remove the salt.

Serving Suggestions

Serve the soup hot as a light lunch or as a first course before a simple main dish. Brown soda bread, crusty whole-grain bread, or oatcakes are good alongside because they can be dipped into the creamy broth without competing with the seaweed. A green salad dressed with cider vinegar or lemon gives the meal a fresh contrast. For a more substantial bowl, add a small pat of butter to the bread or serve the soup with a cheese toastie.

Keep garnishes restrained so the dulse remains noticeable. Parsley and a little black pepper work well; finely sliced scallions are another option. Put lemon wedges on the table for anyone who likes a brighter finish. If serving guests, mention that the soup contains seaweed, since its briny flavor and texture are distinctive and may be unfamiliar.

Variations

Use a different seaweed. If dulse is hard to find, use the same volume of dried wakame flakes or snipped nori as a practical substitute. Wakame gives a milder, softer, slightly sweet sea flavor, while nori brings a toasty note and can darken the broth. These alternatives make a tasty soup but move it away from the specifically Irish dulse character. Add them gradually and taste, because brands and varieties differ in saltiness.

Make it dairy-free. Replace the butter with 2 tablespoons (30 ml) olive oil and use 1 1/2 cups (360 ml) unsweetened oat milk in place of the milk and cream. Choose an unflavored product, since sweetened or vanilla versions will not suit a savory soup. The result is lighter and less rich; mashing some potatoes into the broth helps give it body.

Make a more rustic, non-creamy soup. Leave out the milk and cream, and use an additional 1 1/2 cups (360 ml) stock. Mash a few potatoes to thicken the broth, then finish with lemon and parsley. You can also stir in a handful of chopped kale during the final 5 minutes of simmering, though the greens add their own flavor and make the soup less focused on dulse.

Change the potato texture. Waxy potatoes hold their shape, while floury potatoes break down more readily and thicken the broth. For a smooth soup, blend only after the potatoes are fully tender, then return it to the pot before adding dairy. Blend carefully in batches if using a countertop blender, since hot liquid expands; never fill the jar to the top.

Storage and Reheating

Cool leftovers promptly and refrigerate them within 2 hours of cooking, in a covered container. The soup keeps for 3 to 4 days in the refrigerator. For the best texture, store it without the parsley garnish and add fresh herbs when serving. The potatoes may absorb some broth as the soup sits, so expect the chilled soup to be thicker than it was in the pot.

Reheat only the amount you plan to eat in a saucepan over medium-low heat, stirring often and adding a splash of stock or water if it has thickened. Reheat leftovers to 165°F (74°C), checked with a food thermometer, as recommended for food safety. Avoid a rolling boil, which can make the dairy grainy. You can also freeze the soup in airtight, freezer-safe portions for up to 2 months, though the milk and cream may separate slightly after thawing. Thaw overnight in the refrigerator, reheat gently to 165°F (74°C), and whisk to bring the broth back together as much as possible.

Frequently Asked Questions

What is dulse, and does it taste strongly of the sea?
Dulse is an edible red seaweed sold fresh or dried. Dried dulse has a savory, salty, ocean-like flavor, but the potatoes, leeks, stock, and dairy mellow it in this soup. Start with the amount listed, then add more only if you want a more pronounced seaweed taste.

Can I use fresh seaweed instead of dried dulse?
Yes. Rinse fresh dulse carefully to remove grit, chop it, and start with about 1 cup (30 g). Fresh seaweed is less concentrated by weight and can vary considerably, so taste the broth before adding more or seasoning with salt. Do not use seaweed gathered from an unknown shoreline; choose a product identified as edible and intended for food.

Can I make Irish seaweed soup ahead?
Yes. Make it a day ahead, cool it promptly, and refrigerate it in a covered container. The flavors mingle as it rests, while the potatoes may thicken the broth. Reheat gently to 165°F (74°C), adding a little stock or water if needed, and garnish just before serving.

How can I make the soup thicker without adding flour?
Mash several potato cubes into the broth, or blend a portion of the soup and stir it back in. Both methods use the potatoes already in the recipe and preserve the seaweed flavor. Avoid blending the entire pot unless you specifically want a smooth soup, because a fully puréed texture hides the contrast between tender potatoes and soft dulse.

Is carrageen moss a good substitute for dulse?
Not in this recipe. Carrageen moss, also called Irish moss, is a seaweed commonly used as a thickener and is better suited to preparations where its gelling quality is wanted. It does not provide the same savory, leafy texture as dulse. Use dried wakame or nori if you need a closer cooking substitute, while recognizing that the flavor will change.

Can I make the soup without potatoes?
You can, but potatoes provide much of the soup’s body and make the broth substantial. For a lower-starch texture, replace them with about 2 cups (300 g) diced carrots or turnips and simmer until tender. The soup will be sweeter or more earthy, respectively, and thinner, so you may want to blend a cup of the cooked vegetables into the broth.

More recipes to cook

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

Spotted an error? Tell us and we will correct it (corrections policy).