(The Business Times) - Move over, methamphetamine. There's a new lifestyle drug in town and it goes by the code name of 'golden sand', or as it's more popularly known - salted egg yolk.

All it takes to put you into a state of ecstasy is the sight of that golden, creamy liquid oozing out of a freshly baked croissant or fluffy white bun.

Every second, somewhere in Singapore, someone has a hand stuck inside a bag of potato chips coated with that illicit yellow powder, made more potent with boosters like milk powder, sugar and that other insidious additive - monosodium glutamate.

'Pushers' are minting it, churning out thousands of bags a week to desperate addicts - the bane of family members who find them unconscious in front of the TV from umami overdose. And in the same way that drugs come in varying forms of purity, so does salted egg yolk - you don't know if what you're eating comes from a real duck, or a powder made of 'natural' flavours and permitted stabilisers.

It wasn't that long ago - maybe two years - that Singaporeans' relationship with salted egg yolk was still healthy. We cooked with it; we enjoyed salted egg crab at zichar places; we ate it in traditional mooncakes; at most, we'd flit from one dim sum restaurant to another to find our favourite liu sha bao, or molten salted egg custard bun.

Then one day, something flicked the salty-sweet taste receptor switch in our collective brains and we were inexplicably hooked. We wanted salted egg potato chips and fried fish skins. We lusted after molten salted egg croissants. We put salted egg sauce on everything from fries to McDonalds chicken burgers. The more we wanted, the more purveyors were happy to give it to us.

Jonathan Shen of The Golden Duck - maker of salted egg potato crisps and deep fried fish skins - has been in the business since November last year and estimates he sells easily 5000 packs of both a week. At $7 a bag, do the math. It's good business. Demand is always greater than supply but now that he's got a 3000 sq ft factory to produce the snacks, there are fewer sold-out days, unless there's a big food expo he's taking part in.

Irvin Gunawan hit pay dirt when he gave up his zichar business and focused on his namesake Irvin's 'Dangerously Addictive' salted egg chips and fish skin, selling the plastic bottles (and now fancy resealable bags) at $16 each. They're at least twice the size of a pack of The Golden Duck. Pricey, yet he still imposes a five-packet limit on buyers.

He made enough to move from his coffeshop to a store in Vivocity and open a central kitchen. Even if the craze has levelled off - which he doesn't believe it has - "We've seen steady sales in the Singapore market, but we're seeing a lot more foreigners, so overall sales has increased."

Over at Antoinette, chef-owner Pang Kok Keong rode the wave with the introduction of molten salted egg yolk croissants, and he's just one of many pastry chefs to do so. The craze may have wound down a little, "but salted egg croissants are still our bestseller - we sell over 100 pieces a day". On top of that, his salted egg lava-centered mooncakes were a hit during the Mid-Autumn festival, and even his current salted egg truffles are popular.

So, if there's still that niggling question of why this ancient Chinese peasant fare became the subject of our cravings just two years ago, the answer lies in what we've done to it. Pooja Vig, who runs The Nutrition Clinic, explains.

"Look at how salted eggs were traditionally prepared and eaten - it was served in a simple congee where it can be a nourishing meal. The main concern is when the salted egg trend gets translated into everything from cakes to croissants and ready-made salted egg powder. When we move too far from tradition, we lose health benefits and start adding sugar and processed ingredients."

Not only that, "we're hard-wired to crave salt," says Ms Vig. "It lights up the pleasure chemicals in our brains to make us keep eating it. And when we mix salty foods with sugar and pastries, it's easy to see how addictive it can be - we won't overeat congee and salted egg but we certainly will eat more salted egg croissants and cakes!"

Nothing beats the real thing but with convenience a big buzz-word, it doesn't take long for manufacturers to step in. Knorr, for one, "noticed a creative trend to extend this flavour to new food formats," says Ng Seow Ling, managing director of Unilever Food Solutions (Singapore).

The company launched its salted egg powder in 2014 for commercial use. The ingredients list includes chicken egg, maltodextrin, 'flavourings' and 'colourings'. All a chef needs to do is add water and fry it in margarine to get a salted egg sauce. So whether you're getting the real thing in your potato crisps or salted egg crab dish may well depend on you sneaking into the relevant kitchens to find out.

But as everybody says, the appetite for salted egg yolk shows no sign of ebbing. Especially not as long as there's a business opportunity in it. "It's a bit like cheating," says Ivan Brehm, executive head chef of Bacchanalia, of those jumping on the bandwagon. "In an industry that's as competitive as ours, when one finds something that works, one sticks with it."

It doesn't mean that all chefs want to cash in on the trend. There are those who use it because it works for their food. Chef Brehm grates the yolks to use as natural stabilisers in emulsions, or to add salty umami flavours to pasta dishes. Luke Whearty of Operation Dagger cures egg yolks in sugar and rum to make the bar's signature cocktail.

But whichever way you like your egg yolks, the key is that the next time you reach for a salted egg crisp, you'll know exactly why you need it so much.