Gourmet popcorn explosion: The snack has gone from cinemas to deli counters in just a couple of years

Two years after he retired early, Joseph Sopher was slowly draining his savings and his soul on online spread-betting sites. He had worked for decades as an electrical wholesaler, taking frequent business trips to the US and beyond. One of the few destinations he relished was Chicago, the site of a trade show – and a store that did magical things with his favourite food.

"Dad always used to love popcorn," his son, Adam, recalls. "It was the only thing that got him in the kitchen and when he went to Chicago he used to come back with more and more of it, in unusual flavours such as caramel and cheese."

When the bags from America, the home of popcorn, ran out, which, invariably, they did very quickly, Joseph, now 54, would experiment with his own creations. After retirement, and when the spread-betting didn't work out, Adam says he "cajoled Dad into producing some of the recipes he'd played with years earlier," adding: "then it went crazy".

This was all of two years ago, when popcorn was the stuff cinemas made you eat while openly fleecing you. It was salty or sweet and unhealthy yet so light it hardly seemed worth the bother. It still had nostalgic associations with nice times in cinema seats, so many of us bought it by the obscenely-priced bucketload, but it just as readily conjured images of sticky carpets.

Sopher did as his family asked and created small batches of popcorn made with ingredients that have never been inside a cinema: mirin, soya, chilli, coconut. Joe & Seph's Gourmet Popcorn set up a small stall at the BBC Good Food Show in London in 2010, where the only other exhibitor of popcorn, Adam Sopher recalls, was Tyrrells, the posh-crisps people.

"We were so nervous to see whether people would like the product but within a few hours we had people queuing 10-deep," he says.

In just two years, the Sophers have helped create one of the fastest-growing segments in a highly competitive snacks market. Since his and Tyrrells' test in 2010, a market that was already big in the US, and showed early signs of popping here, has exploded. Such is our appetite for popcorn, from the gourmet (Madras with lime and black onion seed, anyone?) to the barely there health lines, the Sophers expect to turn over £1m this year and have just signed a coals-to-Newcastle deal to export their produce to America.

According to Mintel, the market analysts, outside of cinemas we bought £53m of popcorn last year. That's a pop in the microwave compared to the £1.3bn we spent on crisps, or even the £345m of nuts we guzzled, but represents at least a 10 per cent leap (or 20 per cent, according to other analysts) in just one year and is predicted to be much higher this year.

Boosted in part by the rise of home cinemas and the broader trend for treats in bags designed to be shared (sharing optional), supermarkets report even healthier leaps in sales of popcorn, including microwaveable bags. Sales have nearly doubled in a year at Waitrose, thanks in part to its Heston Blumenthal range, while Tesco has added five new flavours to its existing three. The supermarket's snack buyer, Lee Bannerman, calls popcorn "the biggest success story in the UK snacking market for at least 10 years".

In May this year, Cadbury launched bags of toffee popcorn coated in chocolate, four years after it got rid of the Butterkist brand, which retains a healthy chunk of the near-monopoly it once had on a small market for home popcorn.

But new brands are bringing the fight to the supermarkets and snack giants. Metcalfe's Skinny Topcorn, Diva Popcorn, Peter Popple's, Corn Again, Lord Poppington and Love Da Pop are among those competing with Joe & Seph's.

Tyrrells reports sales of its popcorn lines have doubled twice in two years, to a predicted £4m this year (chasing the £80m of crisps it will sell). "We're pleased consumers have been willing to change the way we think about popcorn," says Tyrrells' Oliver Rudgard. "When we looked at the market two years ago... popcorn was something you only ate in cinemas. We wanted to take it out."

Producers have also battled to beat the perception that popcorn represents a massive rip-off. By some calculations, the buckets we buy in cinemas are marked up by as much as 1,200 per cent, leading to an unlikely intervention last week by George Galloway. The Respect MP told the BBC he has put down an Early Day Motion in Parliament calling for action on the price of food in cinemas.

"It's absolute profiteering," he cried.

Price outside cinemas are generally lower, but a 100g pouch of Joe & Seph's toffee apple and cinnamon popcorn, for example, costs four pounds, far more than a posh bag of crisps of a similar size. "The margins in cinemas are ridiculous because you're just buying corn and putting it in a machine with butter," Adam Sopher says. "Ours is expensive because our chefs make it by hand. We use top quality ingredients including, for example, real 10-year-old whisky."

Nor does Sopher, 27, make great claims about his product's health credentials (many other brands do). Sopher pops his corn in hot air; the resulting puffs are as healthy as they were on the cob, but many other brands pop in oil. Either way, the flavourings add the calories. A hundred grams of Joe & Seph's classic caramel packs 490 calories, while the same amount of salt-and-pepper Kettle Chips has 502. The popcorn includes 23g of fat, to the crisps' 28.6g. Sopher, 27, admits his popcorn is an indulgence and says the family often struggles to resist the mountains of the stuff at their factory in north-west London.

Joseph and his wife, Jackie, 50, work full time while Adam has quit a career in retail consulting to devote himself to the brand. The family now employs almost 20 staff and supply stores including Selfridges, Harrods, Harvey Nichols and Whole Foods Market. They stock the Spanish El Corte Ingles department stores and have just started selling at the Winners and Home Goods supermarkets in North America. Two years after their nervous debut, the Sophers will return to the BBC Good Food Show next month with some of their 24 flavours. Organisers now say they are beating away popcorn exhibitors. It's a long way from sorry business trips to Chicago. "Dad's totally over the moon," Adam says.