Fresh take on the classic burger at Slim's Quality Burgers in Marrickville

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There are many differences to eating burgers at Slim's Quality Burger. Price, freshness, the ability to sit under a light fitting saying "Chomp". But, unlike the ubiquitous global fast-food chains, you do wait for the food. Not for a lengthy time but longer than other "quick service restaurants" where burger patties are flipped onto buns faster than you can say "make that a large fries".

Speed doesn't ruin food but, at Slim's, you can press your nose against the glass window encasing the open kitchen and watch staff toast soft potato buns, wash and hand-cut potatoes for fries, cook beef patties on a grill and stack burgers with tomato slices, shredded lettuce, cheese and pickles.

"Everything comes in fresh, never frozen," says Nik Rollinson, co-founder of Slim's. "We're even churning ice-cream on site daily, throughout the day. We're proud of the equipment, the food product, the ingredients and our production methods."

He's also proud of how clean Slim's restaurants are which, as you survey the sparkling padded red banquettes, curved plywood chairs, chrome-edged tables and red and grey-chequered floors, is notable. Every customer on this afternoon visit takes their wrappings and trays to nearby bins and dutifully following up with hand sanitiser.

One of the main reasons Rollinson co-founded Slim's Quality Burger with Michael Tripp and David Hales, was to take on the big "quick-service restaurant" chains filling the country.

"They obviously own the market share by way of volume and probably sales in Australia and the product is something left to be desired," he says.

There are three Slim's in Sydney, including Marrickville Metro's Smidmore street, and Westfield centres in Mt Druitt and the Sydney CBD.

Our order of a Slim's Original burger, a Deluxe Cheeseburger, a Crispy Chicken Burger, a strawberry thickshake and Coca-Cola spider, plus regular and bacon cheese fries, takes between six and 10 minutes. The drinks come first, followed by the fries, with both ready on the counter when our number is called.

A rookie mistake is filling up on the excellently thick, not too sweet shake, topped with cream and pink as a baby's cheeks, while shovelling in the hot chips with feverish mania. When the burgers are ready, there is still room, but my two young associates' innards are stretched halfway through. Rule one, pace your meal.

Rule two, always order an Original burger. Slim's, in Rollinson's words, is all about the simpler burger rather than the big-as-a-beef beehive, quadruple-decker versions of recent times.

The Original, which features an Angus beef patty, nicely caramelised onions, melted cheese, shredded iceberg lettuce, kicky pickles and Slim's spread made with mayonnaise, pickles and onion, is good stuff. The beef is meaty, the bread is fresh and the flavours do the burger dance of tangy, salady, sweet, peppery and comforting.

The Deluxe Cheeseburger and Crispy Chicken Burger, consumed with passion until their owners lie back on the banquette in belly exhaustion, are also fine. Anyone familiar with fast-food fried chicken should eat Slim's golden fried chicken breast for a new experience.

Valiant members of the table ploughed on with vanilla ice-cream sundaes, flavoured with strawberry and hot fudge, each served in dinky waxed cardboard cups with a lid. Closely inspected, the strawberry sauce was deemed "like jam" by its owner, meaning it was fruity rather than a reddish food colouring replica. The fudge was rich and thick. Both were topped with cookie crumble that might have been behind the ice-cream's "bitty" quality which dissolved on each mouthful.

If there is any particular influence on Slim's it is In-N-Out Burger, the 74-year-old US regional chain with retro decor, drive-in and a cooked-fresh approach. Slim's Quality Burgers outlets in Queensland will soon open with drive-in bays and food delivered to people to eat in their cars. Sydney, Rollinson says, is a hard city to replicate such plans, such is the premium on space.

As it is, the novelty of sitting in a spick-and-span retro diner eating burgers, chips, shakes and ice-creams sundaes, and then being asked to pay under $30 for the lot is unusual and enticing enough.

The low-down

Slim's Quality Burger

Vibe Freshly made burgers, fries and shakes in a 1950s-style diner

Go-to dish Slim's Original with Angus beef, onion, cheese, lettuce, pickles

Average cost for two $25, plus drinks