It's probably fair to say that most of us have never slapped someone so hard with a wet fish that they fall, fully clothed, into a swimming pool.

Until recently, that was also true for Icelandic jazz-pop phenomenon Laufey.

Then she released a song called Mad Woman, whose video required her to hit Heated Rivalry actor Hudson Williams square in the face with a red snapper.

"Oh my God, it was amazing. It was cathartic," she laughs at the memory. "I had a lot of unreleased energy that I released on poor Hudson."

The shoot took place in Los Angeles, with a chic 1960s aesthetic, a superstar cast (including Olympic medallist Alyssa Liu and Katseye singer Megan Skiendiel), and a storyline about Laufey's irrational relationship with a man who's no good for her.

To her delight, the fish scene required several takes, full of improvised insults.

"I'm not a very angry person but it felt good to scream and shout," she says. "I dug into my deepest memories of when I've been the most wronged by men and I accessed a part of myself I didn't know I had in me.

"It felt very primal."

For anyone familiar with the music of Laufey (pronounced lay-vay) Jónsdóttir, primal is the last word you'd associate with her.

Since 2022, she's cast a spell on the charts with swoonsome love songs that mix classic jazz vocals and luscious orchestrations with witty, confessional lyrics.

It's a style she dreamt up while studying at Boston's Berklee College of Music, built on her upbringing in Reykjavik, where she learned piano and cello from the age of four; and a desire to combine her love of movie musicals and Taylor Swift.

When she uploaded her first song, Street by Street - about reclaiming her favourite gardens and bookstores after a breakup - she was stumped when the submission form asked her to list it under a single genre.

In the end, she chose "singer-songwriter". But the question of where Laufey sits in the pantheon of popular music has befuddled critics ever since.

Ask her, and she says it doesn't really matter.

"Older audiences are always trying to figure me out," she says. "Like, 'Is she a jazz musician? Is she a pop musician? Is she a cellist?'

"And I find with my younger audience, they don't have this predetermined bias for what they're meant to enjoy. They listen to what their heart wants to listen to.

"I feel so lucky to be a musician nowadays, because genre has never meant less.

"It's really opened up the road for me to be able to just be all these different versions of myself."

Her latest album, A Matter of Time – released last August – marked the first opportunity to display all her colours.

Themed around the story of a relationship, it's infused with the sound of a ticking clock, counting down to the moment where the 27-year-old's anxieties and insecurities demolish the whole thing.

Along the way, she dips her toes into new sounds – from the soul-infused lead single Silver Lining to the lively Brazilian rhythms of Lover Girl. And it ends with Sabotage, where discordant pianos and jump-scare strings soundtrack her self-destruction.

Significantly, Sabotage was the first song she wrote for the record, before working backwards to the more romantic moments.

"The whole album was a challenge to myself to push beyond my artistic walls, to be a little scared," she explains.

"So that wall of noise, for me, signified breaking out of a traditional mould, both as a human, but also musically."

For the first time, she allowed emotion to override technique. A Matter of Time contains imperfect notes and vocal cracks (within reason, it's not Lou Reed's Metal Machine Music or anything), as the musician exposes her vulnerable side.

It was all inspired by her first experience of falling in love – an experience that was simultaneously thrilling and unsettling.

On Lover Girl, she practically scolds herself for being so reckless. Carousel finds her tentatively revealing flaws to a new lover. A Cautionary Tale is full of post-breakup clarity.

"I gave it too much, I gave myself up / I lost sight of all my dignity."

Without playing amateur psychologist, I wonder if she found love so scary because her background as a classically-trained musician required her to be disciplined and regimented from an early age?

"Certainly, that's a huge part of it," she says.

"My music, I took it so seriously [that I] don't feel like I got to be a regular kid. And it's not because my parents didn't let me or anything like that. I was just like, 'I need to be the best version of myself, and I need to practise really hard'.

"I didn't date, I didn't drink, I didn't do the silly things. I didn't have a rebellious bone in my body.

"So at the age of 20 or 21, when I first started falling in love and learning about life, it felt like pure chaos, because I certainly had not figured anything out.

"I'm still playing catch-up with that. I have so much anxiety about relationships and love and big life events. That's why I write about it so much, because I'm trying to sort out my feelings."

She got the opportunity to explore those emotions further on the recent deluxe version of her album.

It starts with Mad Woman, whose opening instrumental presents a more organised, melodic version of Sabotage's cacophonic climax.

"I'm kind of making fun of myself with that [segue]," Laufey admits. "No-one's noticed it yet, so I'm sitting here waiting, like, 'Come on, nerds, figure this out!'"

The other bonus tracks are more reflective, essentially functioning as a post-mortem on her love life.

"I have this song called I Wait, I Wait, I Wait - and it's about how I'm always preparing for the storm to start, for the person to fall out of love with me.

"[I have] this really innate feeling of instability, so the new songs are quite emotional and introspective."

Laufey says the epilogue was written with the same care as the rest of the album ("it's never just songs that didn't make the original") – making it a definitive version of a record that's already won the Grammy for best traditional pop vocal album.

It put the record back into the UK charts, in the same week Laufey played second on the bill at Coachella and launched a collaboration with the video game Fortnite - a symbol of how she's popped the "trad jazz" bubble to become a generational phenomenon.

That appeal was apparent when she played London's O2 Arena in March.

Over two sold-out nights, she turned the 20,000-capacity venue into a magical playground, kitted out like a fairytale castle. Fans dressed in approximations of her floaty ballgowns and 1920s flapper dresses, hollering lyrics like mantras.

Sitting next to me was a fan, no older than 18, who'd left Cyprus on his own for the first time, determined to see his heroine.

"That's so sweet," Laufey enthuses.

"Who'd have known if a Cypriot boy could have found out about me back in the day? But now, with social media and globalisation, you can find your niche anywhere.

"I think that's why my concerts feel so special, because we're all just collected together from different corners of the world."

It's a spectacle she dreamt about six years ago, sitting on a park bench in Boston Public Garden. Opening her journal, she committed to paper her ambition to make a living as an artist.

"There's something about a park that just gets you thinking," she says.

"I was a student at the time, and hadn't really seen any success yet, but I think there's so much power in writing your dreams down, because at least you've organised that thought."

Last October, she made a symbolic return to that park bench, sweeping away the rust-red leaves of autumnal Boston. As she sipped a coffee, she reflected on those 21-year-old aspirations.

"I absolutely always hoped that I'd be able to make it to this level, but I don't think I dared to write it down," she says. "It just seemed beyond reach."

That's why, as her career keeps hitting new heights, the demands never weigh her down.

"I definitely feel like I'm in the hamster wheel, but not in a bad way. It's just like more and more exciting things keep happening."

And sometimes, if you're really lucky, you even get to slap a man full in the face with a fish.