The phenomenon of the pop-up shop takes a sweet turn as a couple with a passion for cocoa offer up a piece of chocolate heaven

• Richard O'Connor and partner Birgitte Hovmand

"One customer said he'd thought it was a sex shop," laughs Richard O'Connor, 41, the strikingly tall and tanned entrepreneur who founded the company with his elegant Danish girlfriend, Birgitte Hovmand, 39. That customer was not disappointed, though, having found that Chocolate & Love is a pop-up chocolate boutique for the connoisseur, a temporary outlet for exclusive and exquisite edibles, which will melt away again three weeks from now.

"Pop-up" is the buzzword of the moment. All over the UK, recession has left a glut of vacant retail spaces, housing dust and spiders until new leaseholders can be found – not an easy task for any commercial estate agent right now. However, just as nature abhors a vacuum, so entrepreneurs like O'Connor, educated at Glenalmond school and Aberdeen University, cannot pass up low-risk opportunities to road-test a new business – which is why pop-up shops, galleries, bars and restaurants are flourishing.

"We never wanted a shop at all," O'Connor stresses, almost filling the bijou space as he strides back and forth, dropping nibs of astonishingly delicious chocolate into my hands. This founder of successful past Edinburgh businesses Ambergreen and We-Entrepreneurs, he always adored good chocolate but was frustrated at being unable to buy the best of different kinds – nougat, pralines, flavoured varieties – all in the one place. So he and Hovmand, also a chocolate fanatic, combined their business brains with their lusty palates to create a unique fine-chocolate boutique. O'Connor explains: "After six months of travelling, sourcing products from Switzerland to South America – saying 'give us your best chocolate' wherever we went – we came home with 350 different bars and started selling our favourites online at Chocolateandlove.com, which had always been the planned route because of my background in e-commerce."

"Then in early May, at a dinner party in London, I told the woman sitting next to me I was looking for somewhere to put on a chocolate-tasting event. She said, 'Well, I have an empty shop in Edinburgh,' and told me I could have it at a low rent for a few weeks. That was on a Tuesday. On the Thursday I arrived in Edinburgh, picked up the keys and looked at the shop. An hour later, I phoned her to say we'd take it. By 5pm on Friday we had opened."

Pop-ups, as the dynamic and shrewd O'Connor has found, make good commercial sense, enabling retailers to try out new locations and market-test products without committing to long leases or expensive refits. Homeware brand Cath Kidston – whose Edinburgh shop is just a few doors down from the space currently filled with Chocolate & Love – recently negotiated a six-month rental on a vacant site in Glasgow's Princes Square, and has stuffed it with products, from clothes pegs to deckchairs and teacups, in her signature retro prints. Even though her brand is already huge, a pop-up allows Kidston to cautiously test the fashion-forward Glasgow retail scene and see if it will embrace those nostalgic florals to the extent that Edinburgh has. Japanese fashion label Comme Des Garons has taken its own pop-up – the Guerilla Store – to cities all over the world since 2004, including Glasgow, where it popped up 18 months ago. These outlets have remained in each location for no more than a year, selling the label's lower-priced diffusion line, BLACK, and proving massively popular.

Yet pop-up retail is not all about high-end designers and luxury goods: even ubiquitous brands, such as Marmite and HMV, have adopted the pop-up approach over the past year, to test an untried site or shop format. For customers, it adds a sense of excitement to the shopping experience – their feedback and whether or not they subsequently recommend it via word of mouth, Twitter or Facebook is crucial to the retailer, because there's usually no advertising or PR budget to publicise pop-up ventures. The fascination inspired by its ephemeral nature – like the mayfly that lives for a day – is what makes it a must-see.

Equally elusive are the treats to be found at Chocolate & Love, an irresistible haven which manages to indulge all five senses. Fat, creamy roses bloom in black vases, interspersed with votive candles, peacock feathers, even a pair of sexy leopardskin stilettos that would doubtless catch the eye of Theresa May, on tables draped with tactile leather. More provocative posters are pinned on the walls; ambient music plays softly: this place is to sweet shops what Agent Provocateur is to M&S's knicker racks.

Most of the chocolate bars here you're unlikely to have seen before. "This Wild Amazonian bar you won't find in any other shop in the UK," O'Connor says, "but give it to someone to taste and watch their eyes light up." There's Amadei from Italy; Beschle from Switzerland (which the couple discovered on a skiing holiday); the fair-trade and organic Pacari, and Edinburgh's own exquisite Chocolate Tree. Raw chocolate by Conscious, prepared by a process during which the cacao is never heated higher than 47C, is rich in magnesium, high in antioxidants, low GI and yet utterly delicious. O'Connor describes the Love Potion version as "pure Viagra", and its Mint Hint flavour tastes divine, despite being practically a health food. Everything about this place will confound your expectations of chocolate, and that includes prices: you can pay 2.90 for a 100g Crushed Diamonds organic truffle bar with cocoa nibs, or 49 for 50 truffles in a plain wooden box tied with plain string and sealing wax. "But they're the best you've ever tasted," says their purveyor.

We carry on sampling. Jane, the photographer, claims she has never liked licorice – a hugely popular sweet in Denmark, where the couple live for half of the week when not in London – yet she is reduced to a whimpering wreck after tasting a Lakrid chocolate-coated licorice ball, and begs for another. My personal nirvana is the Beschle chocolate nut spread. It's like a celestial Nutella for grownups, and as a tiny spoonful melts against the roof of my mouth I believe I can hear angels singing. There is only one jar of it in the shop, and as it's whisked away the thought that I may never taste it again makes me want to cry. How can such simple bliss exist?

"There are some 400 different flavours in chocolate, but most of the stuff sold nowadays is so bad," he says. "The beans are roasted at such high temperatures, you end up tasting just one flavour and a lot of sugar. For the connoisseur, it's got to have the right balance.

"A taste for chocolate is something you develop," he adds, "the result of an ongoing love. It's like wine, a fascinating subject. Our palates are pretty discerning now, but the beauty of it is that it'll take us years to try everything."

Has opening a pop-up shop given fresh insight into his latest business, I wonder, or is it simply a novel way of guiding customers to the website?

"It's been a real eye-opener," he admits, "because when you're on the other side of a computer screen, I can't see your reaction to the chocolates in the way I can here.

"We'll definitely do more pop-ups, either here, in London or in Copenhagen – maybe three weeks before Christmas, a fortnight before Valentine's – because this is teaching us very intensely about getting new customers and we're teaching people about chocolate, too. We've got three bright young boys and girls out on George Street today saying 'Try some'. You give people chocolate and they go 'Wow!' then they're straight in the door. If we just sit here waiting for people to come in, it won't happen."

His enthusiasm is as addictive as his wares and innovation is in constant flow. What else can we expect to see during the shop's short life? "Hot chocolate," he says, "the really thick sort you get in France. I'll put a few more tables and chairs in the window, get even more people in…"

Looking out at the dazzling blue sky and the passers-by in their shirt sleeves and cotton dresses, I think to myself that if anyone can sell mugs of molten chocolate in high summer, it's this man. Get it while it's hot.

Chocolate & Love is at 46 George Street, Edinburgh until 11 June, or see www.chocolateandlove.com