Blend good butter with dulse or kombu for a deeply savory seaweed butter. The complete recipe, the best seaweeds to use, and dozens of ways to serve it.
Seaweed butter is a compound butter made by blending soft, high-quality butter with dried seaweed — most often dulse, kombu or a blend — until the two become a single, deeply savory spread. It takes ten minutes, needs no cooking, and delivers an umami depth out of all proportion to its effort. Spread it on warm bread, melt it over roast potatoes, finish a steak or a piece of grilled fish with a medallion — once you have a log in the fridge, you will find reasons.
Compound butters are an old French technique for carrying flavor, and seaweed happens to be one of the best things you can carry. Brown and red seaweeds are naturally rich in glutamates — the amino acids behind umami — as well as minerals that read as saltiness without needing much added salt. Fat is the perfect delivery system for both: it coats the palate, slows flavor release, and amplifies aroma.
There's also a texture logic. Dried seaweed, rolled into butter, softens very slightly as it sits, going from flaky to pleasantly chewy-flecked, like fine herbs. And visually, a good seaweed butter is genuinely beautiful — deep red dulse petals or dark kombu dusting suspended in pale gold.
The seaweeds themselves are remarkable organisms. Dulse is a red alga hand-harvested from North Atlantic shores for centuries, while kombu is the umami queen of the brown kelps. Both transform in butter, but differently — which brings us to choosing your seaweed.
Dulse (my top choice). Fruity, savory, faintly smoky, with a natural reddish-purple color. It needs no grinding — just crumble. The most beginner-friendly seaweed butter, and the prettiest.
Kombu, ground. Deeper and more marine than dulse, with pure glutamate intensity. Grind dried kombu to powder in a spice grinder. Use a lighter hand than with dulse — kombu's flavor is more concentrated.
Nori. Toasty and familiar; produces a milder butter that's excellent with eggs and potatoes. Buy pre-toasted nori and crumble, or toast sheets briefly over a flame yourself.
Wakame, ground. Mild and green-flavored, best combined with something stronger. Avoid pre-salted or seasoned seaweed products — you want to control the salt yourself.
A blend — say, two parts dulse to one part kombu powder — gives you dulse's fruit and color with kombu's bass note.
Yield: one log, about 16 generous servings.
That's the whole recipe. The technique is simple; the variables worth understanding are below.
Butter quality is the ceiling. Seaweed butter is 90% butter, so use the best you can — cultured European-style butter with its higher fat and slight tang is magnificent here. Salted butter works in a pinch; just skip or reduce added salt.
Don't skip the rest. Freshly mixed seaweed butter tastes like butter with seaweed in it. Rested seaweed butter tastes like one unified thing. Overnight is even better than 30 minutes.
Grind kombu very fine. Coarse kombu fragments are tough and papery in butter. A spice grinder, thirty seconds, done. Dulse, by contrast, wants to stay flaky — its soft leaf texture is part of the charm.
Acid lifts it. A small amount of lemon juice, yuzu zest, or even a drop of sherry vinegar brightens the richness and makes the seaweed flavor read more clearly. Don't overdo it — the butter should finish savory, not sour.
Buy from suppliers who can tell you where and how the seaweed was harvested. The best dulse comes from the wild North Atlantic coasts of Ireland, Maine and Atlantic Canada; the best kombu from the farmed longlines of northern Japan and Korea. Seaweed aquaculture is one of the lowest-impact food systems on Earth — no land, no freshwater, no fertilizer — and responsibly managed wild harvest can be similarly light. It's exactly the kind of supply chain our Tidewright Harvest program is built to support, and our seaweed farming guides explain how these crops are grown.
Yes — simmered kombu from a dashi batch can be minced very fine and folded into butter. It has less punch than dried powdered kombu (you've already extracted much of its glutamate), so use more of it, and squeeze it quite dry first or the butter will weep.
Most people find dulse butter familiar and pleasant — more "savory" than "fishy." Kombu is more oceanic. If a household member is seaweed-wary, start with nori butter (toasty and mild) or use half the dulse quantity.
Yes. A good block-style vegan butter substitutes well; choose one with a high fat content and neutral flavor. The technique is identical. Coconut oil is not a great substitute — its flavor competes with the seaweed rather than carrying it.
Two culprits: the butter was melted (rather than merely softened) when you mixed it, or the seaweed carried residual water. Keep softened butter below its melting point, and always use fully dried seaweed.
Refrigerated in a sealed log, about 2 weeks — many seaweeds contain natural compounds that slow oxidation, so it can keep a little longer than herb butters, but treat two weeks as the safe mark. Frozen, three months. If it smells stale or the color dulls dramatically, make a fresh batch; it only takes ten minutes.
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