It's been many months and dozens and dozens of versions in the making, but one of the most challenging dishes the head chef of Dinner by Heston Blumenthal says he has ever created will be unveiled in Melbourne on Australia Day: a dessert built on the 95-year-old Australian staple Vegemite.

When I first tasted an iteration, on a winter's evening in Melbourne last August, it looked simply like a scoop of ice-cream on a wafer. But this is one of the most celebrated restaurants in the world from one of the most celebrated chefs, so it was never going to be your run-of-the-mill dessert.

By August, group executive chef Ashley Palmer-Watts and head pastry chef Dan Svensson had been working on it for five months. Little did they know it then, but the finished product was still many months and tens of versions away. When I caught up with Palmer-Watts again in London a couple of months later, it was still a frustrating work in progress.

It's hard enough to transform an iconic Australian breakfast spread into a Michelin-star-quality dish. It's doubly tricky when it's being created on the other side of the world by an Englishman (Palmer-Watts) and a Swede (Svensson) for a parochial home crowd.

"It's Vegemite in Australia, we have to get this right," says Palmer-Watts. "If it's not great, we'll be nailed for it."

In August, Palmer-Watts had warned me not to expect something you'd spread on your toast. The ice-cream component, adapting a brown-bread ice-cream recipe, had a malty, salty, chocolate caramel taste with an unmistakable Vegemite note. But the final dessert comprises several components, and it is these that Palmer-Watts and Svensson wrestled with.

Palmer-Watts walked me through their experimentation with texture and form. Early on, they toyed with their Beekeeper's dessert of stout and nutty chocolate ice-cream with honeycomb puffed wheat, malted toasted barley mousse sprayed in yellow chocolate, and a honey centre. Another time, they messed about with a burnt honey tuile on a bohemian cake of chocolate and citrus.

A more recent version comprised the ice-cream with Vegemite yeast syrup on salted butter caramel with pear, olive oil cake and liquid centre of verjuice curd. On top of all that there was burnt honey, caramelised puffed wheat and Tasmanian mountain pepper.

"It's still too busy," he confessed. His visit afforded a breather from the British kitchen lab to canvas the Melbourne team for some local input. "It just needs to be stripped back … say from 10 elements to six."

Fast-forward to the Australia Day lunch menu and the Vegemite ice-cream will include yeast caramel, toasted barley chocolate ganache, macadamia, puffed spelt and sourdough crumble, biscuit, a verjuice and grapefruit gel, and a final Vegemite/barley/malt extract drizzle.

And even then it's likely to be further refined before becoming a fixture on the menu.

But there's more to this story than nailing a dish. The evolution of the Vegemite ice-cream dessert provides a fascinating insight into how Palmer-Watts juggles restaurants at opposite ends of the globe – in two countries historically entwined but one with a much younger culinary tradition.

The London restaurant, in the Mandarin Oriental Hyde Park, grew out of a British culinary history that had largely been forgotten – dishes like Rice & Flesh (c1390), Salamagundy (c1720) and Frumenty (c1390). The Melbourne offshoot at Crown has embraced many of these dishes, but tailored to local conditions and ingredients. In London, Rice & Flesh is made with calf tail; in Melbourne it uses curried kangaroo tail.

Palmer-Watts has been working with Adelaide food historian Barbara Santich to develop dishes here that delve more deeply into Australian history. "We're working on things here that strike a chord with Australian food culture … [but] with a British influence," says Palmer-Watts, who is in Australia several times a year.

So far, this process has produced more sweet than savoury dishes. First came an interpretation of our lamington, also referencing 1808's Rum Rebellion with a white chocolate and rum mousse. Then, to coincide with the Melbourne restaurant's first birthday last October, Palmer-Watts added Eggs in Verjuice, based on a 1730 British recipe but with the chocolate shell styled on an emu's egg.

Most recently, he introduced Cherry Isle Bar: Essentially a reimagining of our Cherry Ripe chocolate bar, it is chocolate mousse, coconut sponge, cherry jam and gel, and almond and bay-leaf ice-cream. Created by MacRobertson Chocolates in 1924, Cherry Ripes themselves also have a British link: the name can be traced back to the lyrics of the 17th-century song Cherry-Ripe by English poet Robert Herrick.

Complicating the pan-global development of these dishes are the huge differences in fresh produce. "When you develop a recipe in the UK, it tastes completely different in Australia, especially pastry," Palmer-Watts explains.

The challenge is only one part of a bigger production that is likely to spawn more Dinner by Heston Blumenthal outposts down the track. While Palmer-Watts says a restaurant in Asia makes "perfect sense", he likens running the operation to anticipating moves in a chess game two years ahead.

Most crucial is developing a pool of talent. "You need to identify who's got [the talent] … and help them get there," he says.

NEED TO KNOW

Australia Day lunch Four courses with matching wine ($270 a head) at Dinner by Heston Blumenthal, Crown. Book at crownmelbourne.com.au or dinnerbyheston.com.au/reservations

Dinner by Heston Blumenthal, Crown Crown Towers, Level 3, 8 Whiteman Street, Southbank, Melbourne. For reservations, call +613 9292 5779

Dinner by Heston Blumenthal, Mandarin Oriental Hyde Park 66 Knightsbridge, London. For reservations call +44 20 7201 3833 or email molon-dinnerhb@mohg.com