"I have no idea how you're going to eat that," says my son. He has a point. I consider the big beef burger delivered to our table, a teetering feat of aerodynamic physics* with a beef patty, cheese, bacon, egg, onion, tomato relish, tomato, beetroot and rocket stacked high between a brioche roll.

The only approach I can see is to squash it down with one hand and saw it in half with a knife. This works quite well, and I manage to eat it without too much indignity.

Harryfields opened in late April at Mosman Bay ferry wharf, taking the place of the long-running Wharfy's, which lost its prime spot when the wharf was renovated. Wharfy's was old-school, an unreconstructed coffee shop that last time I was there did a solid bacon and egg roll. It's a bit similar to your favourite local bar getting a slick new refurb. It might be more comfortable and easy on the eye, but you can't help missing the original.

Harryfields isn't exactly slick. The simple fit-out has striped timber-topped tables, a few citrus trees in pots to demarcate the cafe area, and some shelves holding water bottles and glasses, salt and pepper grinders, and newspapers and magazines, making it easy for customers to help themselves.

Glancing at the menu, however, it's clear Harryfields is new-school. Eggs are free-range, bacon is nitrate-free, potatoes are organic Nicola, brioche buns are from Bourke Street Bakery's Bread and Butter Project, the feta is Meredith, the yoghurt is Barambah, and the Reuben toastie is made with six-hour slow-cooked organic beef brisket.

It's all rather Portlandia, but it also reminds me what I love about Sydney food. That you can sit down at a tiny cafe with a tinier kitchen on a public ferry wharf, staffed by people who look about 12 but legally must be a bit older, and eat food that unselfconsiously grabs flavours from everywhere to create something memorable.

The potato rosti comes with a pile of sweet jamon, two poached eggs and wilted spinach, topped with a good dollop of kasaundi. The spicy Indian eggplant relish teamed with the other flavours rockets the whole thing up a level, even if the rosti are a bit underdone on the inside. 

Baked eggs come in a small cast-iron pan with chorizo, cannellini beans and chickpeas with feta, rocket and sourdough toast. The dense, rich tomato sauce overwhelms the eggs somewhat, but it's a satisfying dish.

The seven-year-old, ever predictable, wants a bacon and egg roll, hold the avocado, organic spiced tomato sauce, aoli and mixed leaves. That leaves a pile of the nitrate-free bacon and two free-range fried eggs on a brioche bun. "That bacon rocks," he says, and puts the whole thing away in double time.

The burger is good, especially with a frothy chocolate milkshake in a milk bottle on the side, and the coffee is smooth and buttery with bite but no bitterness. The first one is a little on the cool side, the second is just right. The organic teas, served in stylish Forlife pots, are by Somage, with a selection to keep black and herbal tea drinkers happy. There's also serious Mork hot chocolate, and the iced coffee, made with a double ristretto and vanilla bean gelato, is an adult indulgence. Even the cola, from Daylesford and Hepburn Mineral Springs Co, is organic.

Service is sincere and helpful, but it would be interesting to see how the kitchen copes on a busy day. We are here on a fairly gentle public holiday with a few other tables around us, including one where an entertaining baby is playing the drop-the-bottle-on-the-ground-and-see-how-many-times-mum-and-dad-will-pick-it-up game. Hours of fun.

Harryfields' owners, Adam Harrigan and Andrew Mansfield, already have solid cafe experience on the Central Coast, with two branches of Oomph at East Gosford and Avoca, and are eager to become part of the local ferry commuters' routine. As of last weekend, Harryfields is open seven days. 

The view over Mosman Bay is one Margaret Preston, who lived in the area for many years, used repeatedly in her work (Mosman Art Gallery up the road has some fine examples). As a ferry rumbles in, a racing yacht glides by, and the reflection of the sun on the water dances on the roof above us, it's hard to think of a better place to be.

* I'm not sure if that's correct but it sounds about right.

THE LOW-DOWN
THE PICKS Potato rosti; big beef burger; iced coffee.
THE COFFEE Pablo and Rusty's
THE LOOK Simple but stylish
THE SERVICE Youthful and sincere