Globe-trotting gastronomy: Out to sea in Norway with the 'mad Scot' who has helped make sea urchins fashionable

For years now, the Danish chef René Redzepi has been telling me about a mad Scot who lives way up in the Arctic Circle on the coast of northern Norway and supplies his restaurant, Noma, with the most exquisite sea urchins. You always know when René is really excited about produce because the hairs on his arms stand up. When he talked about these sea urchins, he bristled like an excited grizzly. Eventually, I got to taste them for myself in the "beachscape" dish at the world-beating Copenhagen restaurant, their pale-yellow innards dried and scattered across frozen pebbles with herbs and raw shrimp in imitation of a beachscape.

I hosted the MAD Foodcamp Symposium in Copenhagen last summer. Among the hundreds of chefs and food producers who attended was the mad Scot himself, Roderick Sloan. We got chatting about our shared love of sea urchins, and he asked whether I'd like to go snorkeling for them with him. "Sure," I said. "How about February?" he replied.

I don't really swim – more "not drown" – and have an embarrassingly low tolerance for cold. But ask me in August if I want to go swimming in the Arctic in February? Sure, bring it on! So, six months later, I fly to Bodo, then take a high-speed catamaran for an hour or so further north to the fishing village of Nordskott where Sloan lives.

"Sea urchins are one of the oldest things in the sea," he explains as we wriggle into our dry suits. "And humans have eaten them for more than 3,000 years. There are mosaics in Pompeii with them in." The mind boggles at the desperation of the first person to break open one of these prickly black balls and scoop out the five "tongues" – in reality, their gonads – inside. But, equally, I would love to have seen his face when he experienced their delicate, sweet, iodine flavour. "As if mermaids made vanilla ice-cream," as a notable food writer (me) once put it.

Today, they are among the most costly seafood. Sloan sells his for around £15 per kilo, but I've paid more than three times that in Paris markets. As is often the case once a sea food is commodified, urchins are often dredged and over-fished. Sloan harvests his beds on a five-year rotation, and only by hand. The best, he finds, grow on exposed rocks in rougher seas. They like the aeration, but this is also the most dangerous place to dive. "A big wave can push you upside-down into the rocks and you can end up not being able to see your oxygen bubbles," he says. "I've had white-outs where I've floated for five minutes not knowing where I was."

It's time to enter the water. Despite my protests, Sloan refuses to let me have gloves or hat. "I want you to really feel what the water's like," he laughs, sadistically. The dry suit keeps the cold at bay for the first few minutes, and we are able to snorkel in the extraordinarily clear waters, spotting the familiar black shadows of the "krakebolle" (Norwegian for "crow's balls") on the sea bed. Soon, though, I begin to lose feeling in my hands and face and, by the time I come out of the water, the former are aflame with pain.

"They thought I was crazy," Sloan tells me when I ask him about the locals' initial reaction. "They are not a traditional catch in north Norway. But the sea here is so clean and cold, things grow very slowly, which means they taste better, and there is so much algae for them to eat."

When his Paris wholesaler went bankrupt in 2008, Sloan was on the verge of giving up. Then Redzepi came to see him; Noma effectively saved his business, and he now sells to a number of restaurants in the region. "I like to think of myself as a kind of underwater talent scout," Sloan says, showing me some of the other amazing shellfish he catches, including new discoveries such as meaty mahogany and unbelievably sweet soft-shell clams. "Starfish is a big debate at the moment. It's eaten in Japan, I know there's potential. But the next thing I really want to get people eating are sea snails. They are my favourite seafood."

"I thought I respected this product before I came here," Trevor Moran, one of two chefs from Noma who has come along, tells me that evening in the kitchen of Nordskott's village hall. "But to see Roddy dropping off a boat into water with ice floating on it is incredible."

Using scissors, Moran shows me how to cut around the sea urchin's mouth and gently scoop out the pale yellow tongues. He combines them with slow-cooked scrambled eggs and dill. Sublime. I pick up a live sea urchin. It begins to move across my palm. I am afraid I might have squealed like a little girl. Sloan takes it from me and places it tenderly in a polystyrene box with the rest of our haul.

"You seem genuinely fond of them," I say. "I spend every day with them," he responds. "I have bits of their spines embedded in various parts of my body. I came here to make money from them years ago; then I fell in love with them."

Michael Booth's latest book, 'Eat, Pray, Eat', is published by Jonathan Cape, priced £14.99; michael-booth.com