The festival, which is the biggest of its kind in Australia and one of the top of its kind in the world, visits Sydney, Melbourne and Auckland, and Canberrans can also get a smaller taste when the GABS Festival comes to Canberra on June 3 at The Durham.

Each year, brewers are asked to produce a unique festival beer. Past years have included beers with belly-button lint, whale vomit, and this year there's one with bone marrow.

Pact Beer Co has taken the liquid dessert angle, teaming up with Melbourne's Butterbing Cookie Sandwiches to make a salted caramel porter delightfully titled 'Who Poured the Porter in the Cookie Jar'.

Pact's Kevin Hingston met Trevor Stubbs when they were working together in IT, and Stubbs' partner Simone Clark was baking as a hobby in her Thermomix. Stubbs and Clarke moved to Melbourne, and started selling treats from an honesty box on their porch. Due to the popularity of their cookie sandwiches, Butterbings was born.

"We've been talking about brewing a Butterbing beer for ages, but Trev was very keen that we use actual cookies, rather than a beer in the key of butterbing," said Hingston.

"Dairy is a big no-no in beer brewing, and I was pretty resistant at first. The first prototype brew was absolutely nuts, with my chiller becoming clogged with cookie bits, but the end result was actually really tasty."

The final product is a drinkable beer with subtle flavour sensations of rich, salted caramel cookies, and everyone who buys a glass of the beer at the festival gets a cookie sandwich, while stocks last.

"While we did use 20kg of the Butterbing salted caramel sauce and a few kilos of whole biscuits, a lot of the velvety cookie sensation comes from using 30 per cent oats in the mash and carbonating with nitrogen - the same gas you find in Guinness and other stouts," said Hingston.

"The carbonation helps cut through that 'dairy slick' that we certainly noticed during the fermentation - another reason why people don't brew with dairy products normally. It was quite an undertaking to get the slickness off the brewery floor, hoses, and tools."

It's the third year at GABS festival for Pact, and in the past they've brewed a quince hefeweizen, and the Pact with the Devil Belgian IPA which is about to come back as a seasonal beer.

After the event, Pact will have a limited supply of kegs of the special brew for wholesale, and it will be available at the GABS Comes to Canberra event.

But don't expect to see it making regular production.

"The cleanup was insane and the cost of cookie sandwiches that went in would make any CFO cry," said Hingston.

Pact won't be the only ones flying the flag for Canberra brewing at the festival.

BentSpoke Brewing Co have created 'Joe Carb', a beer to, "keep you nice and puckered up whilst keeping you trim," and Capital Brewing Co have brewed 'Double Double', a double dry hopped DIPA with a serious hops punch.

The GABS Beer, Cider and Food festival is on in Melbourne on May 19, Sydney on May 27 and Auckland in June 16. See gabsfestival.com.