Secret soup recipe the key to spicy success

Do you chase a chilli high? Love your tastebuds to ping and nostrils to burn? Get on down – literally – to the subterranean DoDee Paidang, a rambunctious, all-day Thai eating house that runs flat-stick from brekkie to the mop-up-booze-stop on the way home. This joint jumps, and how, packed with a mostly Asian crowd of hungry diners.

It all started with a soup recipe that cost more than $10,000, bought by owner Somporn Phosri a few years ago.

Phosri grew up in Udon Thani, the capital of Thailand's Isan province near the Laos border, where his mum ran a local restaurant. She'd head to the market at 2am while Phosri and his sister set up the restaurant before school.

"It had to be perfect or we'd get in trouble," he says. "Then at 4pm, I'd have to help again until eight or nine o'clock. When I was young I hated the restaurant. I wanted to play with my friends."

A rebellious Phosri high-tailed it to Australia when he was 18 but, with limited work options, started cooking his way around Sydney's Thai kitchens.

On a trip home to visit his mum, he noticed Thailand's hugely successful DoDee Paidang restaurant chain, with punters queueing for its soup noodles. Phosri negotiated to buy the recipe, adapting and trialling the soup for months – using Australian ingredients to create a tangy, sweet-sour, pork-based broth, the bones simmered with garlic and coriander root – before opening his first restaurant in 2012. "I can't tell you what I put in it but it's similar to my mum's soup, but my mum's has no lime," he says.

"Even I don't know that recipe," says Boon Low, who co-owns the largest DoDee Paidangs (Sydney is home to five and Melbourne's first opened last year). "Only two chefs here know how to make it. Other restaurants have tried but no one has been able to copy it."

Choose your noodle – glass, rice, egg, instant, and more. Choose your chilli ranking (one to nine), from "DoDee Nursery" to "DoDee Devil" to "DoDee Super Nova". Number three starts with bravado. You think, "I could have gone hotter", but the deeper you slurp, the more your eyes water and sinuses burn. It's rockin'.

"Some Thai restaurants will open up a tin of curry paste but all our curries and sauces are made from scratch," Low says, clearly proud of the approach, and the "special menu" skews towards offal – pork liver salads, and beef tendon soup.

"I'm totally anti-fusion ... and I don't think Thai food should be expensive. It should be affordable and accessible. It shouldn't be made sweet. It should be made how it is in Thailand."

There are beers on tap, free-to-air TV on multiple screens, and poppy, live music most nights. DoDee is a knock-in, knock-out sort of place. It's loads of fun with a party vibe, kind of like Thailand itself.