There’s a bungalow I pass sometimes, and if I pass it around 5pm, the window might be slightly ajar to stop it steaming.

Maybe a tap’s running, and someone I’ve never seen is probably whistling as they begin to cook an early dinner.

Oh, that smells good, I think.

I don’t know who’s in there or what kind of food they favour, but I’m hit by the warmth and familiarity of the first steps of someone else’s meal.

Maybe I’m reading too much into it.

It’s just the smell of frying onions.

The smell of frying onions is normal and ordinary. It’s nothing but a first stop in a dinner with a flashier destination.

What we overlook is that the smell of frying onions – as they brown, as the sugars come free, as they soften – is much more than a smell.

It’s a scene-setter. It’s a statement of intent. It’s the signifier that good things are coming your way.

It’s the first elongated note in an arena as the guitarist walks on and the huge crowd cheers and you know the rest of the band are coming.

It’s the groundwork and the paperwork done. It’s the propellers starting and the trip beginning.

Now – powered – we can fly anywhere we choose. To India. France. To Morocco.

The smell of frying onions is the smell of potential.

At home, not long ago, my pan was on when the doorbell rang and interrupted my own whistling.

Oh, that smells good, said the Amazon man.

It was just frying onions.

But I wonder where it took him.

“That smell takes me back to Minori,” says Italian chef Gennaro Contaldo. “It takes me straight to my home village.”

The smell of frying onion is a passport.

“I would smell the onions beginning when returning home from school,” he says. “Shops and businesses shut, everyone was sitting around tables waiting. I would smell the wonderful aroma; this cooking wafting through my entire village. And as I hurried home to have my meal, and as I passed each window, I wondered what each household was having, too.”

Onions, sending out smoke signals: something great is coming.

“It always makes me hungry,” says Contaldo, whose larder is still packed with those onions he grew up on. “White onions, brown onions. Shallots. I love the red tropea.”

His history proves that “the smell of frying onions is a smell that means a dish is now beginning, and in the Italian kitchen, onions are part of the sofrito, with celery and carrot, and with a little butter, a little olive oil, that smell is, well, heavenly. It always takes me back.”

It takes me back too. To fairgrounds. Late nights.

To the smell of frying, sauteing, sweating or caramelising onions floating over freezing football fans who flock like it’s a pheromone.

It takes me to long wooden tables soon to be packed with family and bolognese. To near that casino on Leicester Square at 1am; to the burger van at that festival where I really should have lined my stomach first; to risotto and stir-fries and almost every generic homemade curry.

It takes us all to very specific dishes, too.

“Onion soup!” says Michel Roux. “That lovely smell, that aroma, that colouring, that caramelisation would lead me to a classic soupe à l’oignon. That dish celebrates everything that is wonderful about onions. But the secret is quality onions. I use roscoff, from Brittany. And take your time. Slowly cook, fry, and they get that lovely golden sweetness. And then you pour your wine or your cider in there and cook that off with stock and what you’re left with is the most glorious onion soup. And that soup, on its own, is a celebration of onion.”

Isn’t it a compliment to the undervalued onion that a man who from toddler age was sitting in the corner of working kitchens can still be so delighted by a smell you’ll find on every street and cul de sac if you sniff long enough at dinnertime?

“It also makes me think of the pissaladière, from the south of France. That smell again: onions frying. But they need to be fried for so long that they almost become a jam. And it’s spread either on pizza dough or on pastry. And then crisscrossed with anchovies and olives and then baked in the oven. Enjoyed with an ice-cold beer. I use onions for almost everything. I could eat them raw.”

That said, there are places he’d rather not encounter the world’s best smell.

“Cheap football burger onions. That smell of stale fat and boiling onions. Like the one you get wafting down on cold days; that puts me off. The one you get from, maybe, hotdog stands.”

Abiye Cole runs a hotdog stand. His fortunes were turned around in no small part thanks to the smell of frying onions.

He describes the award-winning Big Apple Hot Dogs, based a stone’s throw from the Arsenal stadium in north London, as “Britain’s No 1 Black-owned business (for hotdogs)”.

When he began, he was just a shy sausage salesman on Old Street who’d set up his cart way too far away from potential customers. He’d simply hoped they might spot him. Sometimes he’d be brave enough to hold up a sausage and “waggle it at people”, but, “I don’t think I could really do that any more.”

Cole had yet to learn the sheer power of his greatest weapon: the smell of frying onions.

“It was transformative,” he tells me. “I wasn’t doing onions at the time. And my mate of 40 years – he’s in the food world, he once hit the head chef at Langan’s with a frying pan – anyway, he brought these onions with him.”

The two got to work. They sliced up the onions. Got them on the griddle. Then butter. Turned up the heat. Black pepper. Dash of soy sauce. Sometimes fresh thyme.

“I could see people notice the smell immediately,” he says. “The onion. The butter. They’d walk past and I’d see them stop. And then I’d watch them turn around and come straight back to me. It was like magic. It just hit them. I never had enough onions. They always wanted the onions.”

Once, the smell proved so intensely powerful that a man ran across the road waving his wallet at them. It turned out to be Dario Cecchini, Italy’s most famous butcher. He couldn’t get enough.

“But it didn’t matter what type of person walked past, what they did for a living – that smell just got ’em. It gets anyone.”

“Onions cross any and all divides,” says Mark Kurlansky, author of The Core of an Onion, as well as the book Milk: A 10,000-Year History. “Frying onions is the smell of savouriness; it’s umami.”

He tells me that because “the onion grows everywhere, in any climate, they cross geographic divides. They cross class divides. Historically [with ingredients] there’s often been a class distinction.”

Even now, he thinks, “the ‘upper classes’ reject raw onions … but every class eats them cooked.”

There’s a house on every street in every part of town with a window ajar and the smell of frying onions warming a passerby.

Kurlansky says that smell reminds him of “onions in rendering chicken fat; that first step in chopped liver”.

His book quotes the chef Julia Child, the author of Mastering the Art of French Cooking: “It’s hard to imagine a civilisation without onions.”

But how do we make sure civilisation appreciates this?

When I contact Greg Yielding, he is at the annual Onion Convention in San Antonio, Texas.

“We always ask chefs to make good food with onions wherever we go,” he tells me, after a long day of talking onions. “Breakfast usually includes a potato dish with onions. Sometimes onions as garnish on meats. We got the idea for onion ice-cream from a hotel in Bakersfield, California and served it to our group.”

Greg is the executive vice-president of the US’s National Onion Association. He’s been in charge of pushing the onion agenda since 2019; he spent the preceding 14 years praising rice.

“We represent the bulb onion industry in the United States,” he tells me. “So we won’t discuss leeks, ramps or scallions.”

He sees the best in each onion, from red (“you can get an amazingly sweet taste”), to white (“packs a punch on Latino foods”) to yellow (“held their own in French onion soup since the royal court of Versailles in the 18th century”). And he is well aware of the ace in his hand when it comes to that frying onion smell; so universal, so appealing, so unifying.

But Yielding wants more.

“We’d like to see more attention put on the onion in restaurants,” he says. “It’s time to think big. Bring it all to the table. It’s been too long since we saw some really innovative work with onions.” For Yielding, the onion as prologue is no longer enough. Onions have done their time as supporting artists. “We want to see the onion in more main menu items as the featured ingredient.”

For Yielding, it’s become personal.

“When I smell that onion frying …” he says, “I think of my meals growing up in the south. I think of good food and good times at the dinner table. Maybe a few trees blowing in the wind at sunset. I think of chicken and dumplings. I think of home, plain and simple.”

And it’s that word – home – that stays with me.

It’s home the smell of frying onions reminded me of, when last I walked past that bungalow with the steamed-up window.

Home it reminded me of, more than the countless burger vans or stir-fries or late-night walks past high-street kebab shops.

School bus, bag down.

What’s-for-dinner, then spag bol and Neighbours.

Like home means frying onions then chicken and dumplings and good times at sunset for Yielding.

Like home means dark bubbling onion sauces or crisp finishing touches for toddler Roux, then just knee-high to chefs.

Or again sofrito for Contaldo (or the first “sign of a sauce, a soup, a stew, a ragu to come”), the kid pounding through his Italian village to find out what he was getting after school.

“That smell, such a joy bringer,” says Roux. “It’s like frying bacon, isn’t it? The smell of frying onions just perks you up. You just think, gosh that smells good. It’s just such a good start to something.”

He sighs, then reaches the same precise conclusion as Julia Child, all those decades before: “Life would be a misery without onions.”

Somebody Told Me by Danny Wallace is published on 9 May (Ebury, £22)