A former home economist is being hailed as a new Kiwi hero after a journalist launched an investigation to track down the original creator of New Zealand's favourite party food - Kiwi Onion Dip.

The Spinoff's Hayden Donnell tracked down the woman, Rosemary Dempsey, to a retirement village in Epsom - but not without some hurdles.

The dip, which has been a Kiwi summer staple since the 1960s, is made by combining Nestle's reduced cream and onion soup mix. However, a company spokesperson initially told Donnell that Dempsey had passed away.

"We understand she is no longer alive. She never married and had no children, so any living relatives would not be close."

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After turning to Facebook, Donnell soon learned he had been misinformed, tracking down Dempsey and arranging to meet the Kiwi legend.

Dempsey's career began at Nestle New Zealand's fledgling testing kitchen in the late 1950s.

A year after she started, market research company Nielsen gave a presentation that showed onion soup was quickly sliding off the popularity chart - and Dempsey was challenged with boosting its sales.

"Her Eureka moment came when she tried one of Nestlé's more obscure products - reduced cream," writes Donnell.

She said, "I mean, if you mixed onion soup and fresh cream you wouldn't get that flavour. And so it was a matter of trying [reduced cream] out, and it worked. It worked very well."

Now, Donnell is championing Dempsey as a new national hero, having "changed the course of New Zealand history".

"It's as Kiwi as pavlova, as much a part of our national identity as jandals or Slice of Heaven."

But while New Zealand (and Nestle) owes Dempsey a debt of gratitude, the former home economist remains humble.

"I'm happy as I am. I have a wonderful life."