Kelp Salsa Verde: The Green Sauce, Greener

Salsa verde — the Italian green sauce of parsley, capers, anchovy and good oil — is already one of the most useful things in a cook's repertoire. Swap a third of the herbs for blanched fresh kelp and it becomes something rounder and more interesting: still bright and sharp, but with a savoury, saline depth underneath that reads almost like the ocean itself got blended in. Because, well, it did.

This is one of the best first recipes for anyone holding a bunch of fresh kelp and wondering what on earth to do with it. It takes fifteen minutes, keeps a week in the fridge, and goes on nearly everything. Here's how to make it properly — including the blanching step that decides whether your sauce is silky or swampy.

Why kelp works in a green sauce

Fresh kelp, once blanched, behaves a lot like a cooked green vegetable: tender, mild, faintly mineral, and happy to be chopped fine with parsley and garlic. Unlike parsley, though, kelp brings free glutamates — the same compounds that make kombu dashi taste like more than hot water — so it doesn't dilute the sauce's flavour, it deepens it. Our explainer on seaweed umami covers the chemistry, but you don't need a lab to taste the difference: a kelp salsa verde tastes like a salsa verde that's been simmering somewhere for an hour.

It also changes the texture for the better. Blended or finely minced kelp gives the sauce body — a slight viscosity that clings to grilled fish and roast potatoes instead of pooling underneath them. If you've made kelp pesto, you'll recognise the trick immediately.

Choosing and blanching the kelp

This step is the whole game. Raw fresh kelp is rubbery and aggressively briny; properly blanched kelp is silky and mild.

Which kelp? Young sugar kelp blades are ideal — thin, mild, widely farmed in cold northern waters, and profiled in our sugar kelp species page. Winged kelp (alaria) works beautifully too. Thick bull kelp stipes are for pickles, not sauce. If fresh kelp isn't available near you, our guide to buying fresh kelp seasonally covers when and where to look, and farmed sources — like the coastal farms Tidewright's Harvest programme partners with — are the most dependable supply.

The blanch: bring a large pot of generously salted water to a rolling boil. Drop in the kelp blades (rinsed of any surface grit) and time carefully:

• Thin blades (sugar kelp, winged kelp): 60–90 seconds. The colour will flash from olive-brown to brilliant emerald — that colour shift is your doneness signal.
• Thicker blades: 2–3 minutes.

Drain, then plunge into ice water for a minute to lock the colour. Squeeze firmly in a clean towel — blanched kelp holds a surprising amount of water, and a waterlogged base makes a thin, weeping sauce. Chop roughly before measuring. Our full walkthrough of preparing fresh kelp has more detail on this whole process, including freezing for later.

The recipe

Makes about 300 ml — a small jar.

• 100 g blanched, well-squeezed kelp (about 60 g raw), roughly chopped
• 30 g flat-leaf parsley leaves and tender stems
• 1 small garlic clove, chopped
• 2 tbsp capers, rinsed and squeezed dry
• 1 tsp Dijon mustard
• 2 tbsp good red wine vinegar or lemon juice
• 120–150 ml extra-virgin olive oil
• Fine sea salt and black pepper
• Optional: 1 tsp of our seaweed fish sauce or 3 anchovy fillets, for the traditional depth note

Method — two roads.

The knife road (restaurant style): mince the kelp, parsley, garlic and capers together on a board until very fine, then scrape into a bowl and stir in the mustard, vinegar and oil gradually. Season. This version has texture and the brightest flavour.

The blender road (weeknight style): everything except the oil goes in a small blender or food processor; blitz to a rough paste, then drizzle in the oil with the motor running until glossy and spoonable. Stop before it's a purée — you want flecks, not baby food.

Either way, taste after ten minutes of resting: the flavours marry and the sauce will want more acid or salt than it did fresh out of the blender. It should be punchy — this is a condiment, not a side dish.

Ratios worth remembering

The grammar of any green sauce is two parts green to one part acid to five parts oil, by volume, plus punchy little things (capers, garlic, mustard) to taste. Keep kelp at a third to a half of the total greens for your first batch; kelp at 100% makes a sauce that's more relish than salsa — not bad, just a different creature, and one with a bigger iodine footprint per spoonful (see our iodine guide if you're eating it daily).

Ten things to put it on

Grilled or steamed white fish, obviously — but also: roast potatoes straight from the oven; charred broccoli or kale; soft-boiled eggs; lentil salads; a steak off the grill; white beans on toast; cold poached chicken; roasted carrots; simply stirred through warm rice with a squeeze of lemon. Once it's in the fridge you'll find uses faster than you can make it.

Storage and troubleshooting

Poured into a jar with a thin slick of oil on top, kelp salsa verde keeps a week refrigerated — the acid and oil preserve it well. It doesn't freeze well (the oil splits and the greens slump), but a batch is small enough that it rarely survives the week anyway.

Too bitter? You over-blanched, or used a blade with the thick midrib still in — trim midribs from older blades next time, and shave 30 seconds off the blanch.

Too fishy? Under-blanched kelp or old kelp. Fresh blades smell like the sea in a good way — clean and ozone-like. Anything that smells like low tide at noon goes in the compost, not the sauce.

Too thin? Squeeze harder. Blanched kelp is a sponge; your kitchen towel is the fix.

Key takeaways

• Blanch fresh kelp 60–90 seconds until it flashes emerald, then ice-bath and squeeze hard — this step decides the sauce.
• Use a third to a half kelp against parsley for balance; young, thin blades (sugar kelp, winged kelp) are ideal.
• Two methods: knife-minced for texture and brightness, blender for speed. Both want five parts oil to one part acid.
• Rest the sauce ten minutes before the final seasoning — the flavour changes as it marries.
• Keeps a week in the fridge under an oil cap; doesn't freeze well; goes on almost everything savoury.

FAQ

Can I make this with dried kelp instead of fresh?

Not well — dried kelp rehydrates to a chewier, more intense product that overwhelms a fresh green sauce. If dried is all you have, soak a small piece in the warm vinegar for 20 minutes, then mince just 15–20 g of it with extra parsley. Fresh or frozen blanched kelp is very much the right tool here.

How long does fresh kelp keep before I blanch it?

In the fridge, well-wrapped, three to five days; in a salted or brined pack as sold, up to several weeks once drained and refrigerated. Blanched and squeezed, it freezes beautifully for three months — our storing seaweed guide covers all the formats in detail.

Is kelp salsa verde safe to eat every day?

In condiment quantities — a spoonful or two — yes for most people. Kelp is iodine-rich, so if you're putting this on every meal or you have a thyroid condition to manage, read our iodine and seaweed article and scale your kelp-to-parsley ratio down.

What oil should I use?

A fruity extra-virgin olive oil is the classic and the right choice; its pepperiness plays well with kelp's minerality. A neutral oil makes a flatter sauce. Avoid anything strongly flavoured (walnut, toasted sesame) — they fight the greens.

Can I add chilli?

Please do. A finely chopped fresh green chilli or a pinch of dried flakes alongside the garlic turns this toward a chimichurri-kelp hybrid that's excellent on grilled squid and prawns.