Making my way through a car park on the outskirts of a city while being utterly drenched by sheets of rain might be a sorry situation. But the city is Copenhagen, which means the industrial estate I'm running through is both beautiful in its grimy, gritty way, and also home to art galleries and Michelin-starred restaurants.
I'm off to meet the quietly magnetic Sandia Chang, who's in the city to take part in the World Hot Dog Championships in a couple of hours' time, and I'm here to shadow her and her husband and fellow restaurateur James Knappett as they represent the UK. Rain or not, who could be sorry about that?

Copenhagen is not a city that does food lightly. Which means that a hot dog contest – which could feel a bit 'village fete' in different circumstances – is put on to exacting standards and with an obsessive eye for detail. It's part of Copenhagen Cooking & Food Festival, a ten-day celebration of the city's eclectic, compulsive food culture. The festival comprises pop-up events, competitions, food tours and Copenhagen restaurants putting on collaborative menus with chefs who fly in from all over the Nordics and the rest of the world. It also complements – although isn't not directly related to – the MAD Symposium, an annual gathering of some of the best-known chefs in the world, curated (of course) by Rene Redzepi.

None of this is new to Chang, she explains to me in Amass restaurant, where she and Knappett are overseeing the prep for the 150 hot dogs they'll give out at the competition and I'm drying out. Both of them lived in Copenhagen together. Chang grew up in LA, worked for Thomas Keller's French Laundry in Napa Valley after training at the Culinary Institute of America, then moved to New York.

"I just packed a bag of clothes and my knives and moved. I had the Zagat guide, I went to the ten best restaurants in New York, and I gave my resumé to those and then I landed a job at one of them," Chang recounts. After suffering burnout from long hours, low pay and not enough time off, she started from scratch at Keller's Per Se, running food from the kitchen while training to be a sommelier. It was there that she met the Suffolk-born Knappett.

They reunited again at the first incarnation of Rene Redzepi's era-defining Noma, long enough ago that Chang remembers the staff struggling to fill the restaurant for lunch. "James and I met at Per Se, and then we got married and then he was waiting for a green card to come through," Chang explains. "So in the meantime he couldn't live in the US. He went and did a stage at Noma and absolutely fell in love with it. And then he's like 'I'm not leaving, I'm staying.' I was like 'What? No, I'm not leaving New York.' At the time I was at the height of my career at Per Se – I was loving it, life was great, I knew everybody in the city. It was just a really great time for me. I was like 'I'm not leaving.' So he worked at Noma for a good year before I came over."

From Per Se and Noma to a hot dog competition might seem like a bit of a strange jump. But Chang's career progression has been unusual, to say the least. Having trained both as a chef and a sommelier, Chang followed up on her dream of opening up a bar celebrating grower champagnes when she and Knappett moved back to London. They settled on a dual concept: a champagne bar that served hot dogs for her, with a hidden restaurant for him at the back.

Hot dogs are the friendliest food. People aren't afraid of them

"I said that I wanted to open a wine bar because I was so done with fine dining after Per Se," Chang says. "And James was like 'There's no way that I'm going to waste my whole career to end up cooking hot dogs for the rest of my life.' He wanted to do something more in tune with how he was trained. So he wanted to do Kitchen Table, and I wanted to do Bubbledogs. And we kept arguing and then we finally decided to split the restaurant in half. So I could have the front part to do what I want and he could have the back part to do what he wants.

People are like 'You're so smart, you share the same overhead costs, you have shared staff costs.' But it wasn't for that reason – it was just because we couldn't compromise. We couldn't agree, so we just agreed to disagree."

Bubbledogs and Kitchen Table arguably work better together than they have any right to. Kitchen Table is full every night, with the occasional cancellation gold dust to the London food populace when it's circulated on social media. It also won its second Michelin star in this year's guide. Bubbledogs, meanwhile, is a standout restaurant and bar even in Fitzrovia, an area that's blessed with its fair share of talent.

"Living in Copenhagen, especially at Noma, we had the best champagne list ever and everything about it was just so real. It was just normal wine. And I was like 'Well I want to create a wine bar that serves great champagne, but feels normal. I wanted to create somewhere where people felt like it was easy – it wasn't just all about the champagne, it was just an easy place to go. And being American, I was just like 'Why not serve hot dogs?' Champagne is amazing with charcuterie; champagne is amazing with cheese; champagne is amazing with french fries – that's one of my favourite combinations – so I just thought, 'Well, the hot dog is the friendliest food; people are not afraid of hot dogs.'"

But if there's one thing that binds these two markedly different restaurants – the body that encases these seemingly split personalities – it's the standards both Chang and Knappett set for themselves. "It's the way we were trained in our career, especially by Thomas Keller," Chang says. "No matter if it's a bowl of peanuts or if it's a £125 tasting menu, it's the same dedication and the same respect to everything. It's a standard. I feel like if I ever slipped on a standard, if I ever decided one day that I was going to be lazy, I would never be able to forgive myself, because I can just feel Thomas Keller behind me, looking down at me."

"It's so ingrained in our in our minds and the way we work. Like everything, it was about the way he taught us. So we were really proud to be able to serve hot dogs with the same ingredients, from the same suppliers that supply Kitchen Table. And we make everything ourselves."

It's why, a few hours before the competition, both Chang and Knappett – who wanders nomadically between the table we're sitting at and the kitchen in an archetypical chef way – are quietly confident. The competition includes chefs from eight international restaurants, including Frederikshøj in Aarhus, Denmark; El Baqueano in Buenos Aires, Argentina (a mainstay in the World's 50 Best Restaurants list for Latin America); and female butchers from the international Butchers Manifesto initiative.

"As long we've had a hot dog restaurant, we've heard about it. Paul Cunningham – a great guy and English chef who has a two-Michelin-starred restaurant in the outskirts of the very west coast of Denmark, Henne Kirkeby Kro, and had a restaurant in Tivoli called The Paul – was always talking about this competition. I think he might have started organising it. I said 'How come we never get invited?' And so this year we were invited. I was so happy. And then I looked at the lineup of chefs and nobody has a hot dog restaurant, and then the pressure became bigger. It's like 'Man, if we don't win, we're gonna look so bad.'"

Chang and Knappett don't collaborate as much as you might think at the restaurants – Chang sources the wine for both and occasionally weighs into the structure of Kitchen Table's tasting menus from a drinks perspective, and Knappett will taste and critique the occasional new hot dog that pops up on the list at Bubbledogs, but aside from that, they're largely separate entities. But their hot dog here is a true partnership, created by both of them. "Whatever we do, even if it's a hot dog, it's the most intricate everything: every sauce, every garnish – everything is thought out. It's like a Michelin-starred plate," Chang says. The result is an American-style frankfurter handmade with British pork, mango chutney, peanut, cucumber relish, yoghurt, coriander and more – every topping designed to hit a different flavour note.

It's not a competitive eating competition, but I try as many as I can...

With that, I leave them to explore a little more of the city's food scene, as I've been doing in the couple of days before. I take a tour around Reffen – a street-food complex around the corner named after the colloquial name of the former industrial district we're in – with its creative director Dan Husted, a big, effervescent Dane with a touch of the Jurgen Klopp about him.

Street food is booming here, and Reffen is forward-thinking, with clever use of shipping containers and a flexible rent structure that prioritises the traders. The food is eclectic (and what I try, from cactus tacos to Gambian peanut stew, is delicious). It's next to a skate park and a beer bar and brewery from Danish brewer Mikkeller. There are elements of Pop Brixton and Street Feast's markets here, but it's identifiably Copenhagen.

Elsewhere in Refshaleøen, Alchemist is rising phoenix-like from the ashes of its old space to become an enormous, three-storey restaurant, aiming to open in early 2019. The infuriatingly young chef Rasmus Munk, not happy with one Michelin star in the old space, is aiming for three and a place on the World's 50 Best Restaurants list once it reopens. The expansive space will do just 45 covers a night and serve one menu, but include a lounge and test kitchen, too, and aim to use it as a mouthpiece to drive conversations around sustainability, organic food and staffing issues – not unlike the position Rene Redzepi's worked himself into.

I have a fantastic lunch at Aamanns 1921, a brasserie-style restaurant from Adam Aamann and an offshoot of the Michelin-starred (naturally) Aamanns, which aims to reinterpret Nordic food, particularly smørrebrød, open-faced sandwiches served on rye bread. And I'm invited to the Freja Symposium, too – a series of talks and panel discussions held in the Nimb Hotel's beautiful Gemyse restaurant by food luminaries in the Nordics that hinge around gender equality in the hospitality industry, where the speakers present a stark reminder of how far there is yet to go. As I said, Copenhagen is a city that's compulsive about its food and about its effect on culture.

It all feels a world away from a hot dog competition, but a hot dog competition is what I'm here for, so I meet the lively marketing director of the festival, Stephen
Kastberg Haar, back downtown. Temporary hot dog kitchens are set up on a closed street between two of the city's leading food halls, with a stage at one end to host a panel of international judges that includes Lara Gilmore, the wife of chef Massimo Bottura, who runs their restaurant Osteria Francescana – voted the best restaurant in the world in the World's 50 Best List – as well as their food-waste charity Food for Soul; and to introduce the competitors and the charity, Top Dog, that's redirecting the funds raised to great causes including CARE Denmark.

It's not a competitive eating competition (despite most people's default assumption when I say I'm going to the World Hot Dog Championships, which probably says more about my lifestyle than them), but I try as many as I can. The Butchers Manifesto dog is simple, letting the meat speak for itself, with just mayo and dried shallots, and it's all crunch and richness; the meat in the Danish effort is beautiful, although fresh fig and chutney make it possibly a little oversweet.

I go and see Chang and Knappett, tinkering with each hot dog to that familiar Thomas Keller standard before it goes out, and maybe I'm biased, but theirs is my favourite: acidity from cucumber relish is tempered by a punch of mango; chilli and peanut sit low in the mix; and the brined frankfurter itself anchors it, with salinity and umami notes coming through.

At the end of the competition, as judges, chefs and diners battle on through that intermittent but drenching rain, the winner is announced. I hold my breath, as I'm sure do Chang and Knappett, who are next to each other on the stage, now packed with competitors as well as judges. It's El Baqueano, from Buenos Aires.

Copenhagen cooking

There are already a whopping 252 events confirmed for next year's festival across the length and breadth of the city. As well as the return of Top Dog's World Hot Dog Championships, there'll be pop-ups, feasting dinners, collaborations, and a mini-festival in the Frederiksberg district of the city, including the Harvest Feast – a long-table banquet set across an entire street. All of the festival's events aim to show off the food culture of this unique city.

Copenhagen Cooking and Food Festival runs from 23 August-1 September 2019. For more information, go to copenhagencooking.com

Afterwards, Chang and Knappett are clearly despairing – chefs are nothing if not competitive, whatever the scale of the competition, after all, especially those trained to Thomas Keller and Rene Redzepi's sky-reaching standards. But whatever they might think in the immediate reaction to the announcement, their visit hasn't been in vain. They've returned to a one-time home that is, even more so in this ten days or so, a hive of activity designed to kick on conversations in the industry at the highest level. They've battled with chefs from across the globe, to diners and judges who I'd say will surely look out for Bubbledogs the next time they're in London.

And there's a strange kinship between them and the city: it's a hot dog championship in the midst of a festival and initiative that brings together some of the most ambitious chefs in the world; where a type of food that's hawked at baseball games and on street corners is given the same level of care and attention as a tasting menu. In that sense, Chang and Knappett are perfectly at home here in the city that once housed them. They'll be back, and I'm sure I will be, too – even if I have to brave a little rain.

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