The Rover's gratin-topped dish is a fish pie for the ages

• $9 for a single oyster? Why prices are skyrocketing at Sydney restaurants

"How much for the oyster, sorry?" I'm sure I heard our waiter say $9, but that can't be right. Rock oysters are about $5 served natural in most Sydney restaurants, or $6 with a cheffy mignonette. "Nine dollars, but it's premium-grade," he says. "You probably won't taste a better oyster in Australia." Hmm. We'll see.

I'm at The Rover in Surry Hills, which was a vaguely Irish whiskey bar – The Wild Rover – until a handsome makeover last April. It's all rough brick, soft lighting, dark timbers and purposely shabby bistro chairs. There are excellent cocktails and a snack menu with one of the city's greatest sausage rolls, but I'm here because the dining room upstairs opened in December, and I've been waiting a long time for a seafood joint like it.

Yes, we have Doyles at Watsons Bay, but it's feeling a bit overripe. Bondi is a breeding ground for breezy seafood spots, while Josh Niland does incredible things with fish at Saint Peter in Paddington. (By the way, Niland's slick new eatery, Petermen, opens next week in St Leonards with – wait for it – a $240 "tuna chateaubriand", designed to feed four. I know, I know: good seafood should never be cheap.)

What I've always wanted is a cosy, British-style seafood joint. The kind of place you can pop into for a fisherman's pie and a stout and be on your way. That wish is now a reality, thanks to "Nick's fisherman's pie" ($26), at The Rover, created by head chef Nick Mathieson and covered with steaming, velvety potato gratin.

It's a pie for the ages. Hunky flakes of smoked trout lolling about in bechamel with blue-eye trevalla and milk-poached sea mullet. A tumble of crisp-fried capers and cured egg yolk provides texture. Add a mixed-leaf salad glossed with tarragon dressing ($12) to your order for the perfect lunch. In lieu of stout, a chilled gamay from Adelaide Hills' Coulter Wines does the trick, alive with snap, crackle and bright red fruit.

But you want to know about that $9 oyster, right? It comes from the sapphire-blue waters of Wonboyn, the last village on the southern NSW coastline. Farming oysters is bloody hard work and producers should be paid accordingly, but how much is too much for something that disappears in seconds?

The flavour of this Wonboyn oyster is long, clean and intensely savoury, though. It sticks around. Lemon is unnecessary, mignonette would be a travesty. The best oyster in Australia? It's certainly the best oyster I've tasted in months. Next time, I might spring for two.

The group behind The Rover – Liquid & Larder – also owns CBD steakhouses Bistecca and The Gidley. British-born executive chef Pip Pratt writes the menus across all three venues, but I sense he's having more fun tapping into his roots here.

There is, for instance, a Bakewell tart coming soon. The jammy, almond-topped frangipane is much rarer outside of the UK than it should be. In the meantime, there's a deeply satisfying stone fruit trifle ($16) for sweets, or a dark chocolate and passionfruit ganache tart ($12) harnessed by faultless shortcrust pastry.

But before any of that: crumpets ($16). Specifically, glazed crumpets served with a wedge of eel pâté and horseradish jelly. Spread it on thick for walloping flavour you can see.

I'm less taken by ribbons of cuttlefish swamped in almond gazpacho ($18) with spikes of black garlic aioli that mount an all-out assault on the delicate mollusc.

A gently cooked fillet of groper ($59) has the opposite problem. It needs more seasoning, more punch – a reason to exist beyond looking pretty in a pil-pil missing the weight of garlic required for the Basque seafood sauce.

Whole flathead ($40) is a brilliant display of kitchen talent, though, with blistered and golden, pan-seared skin giving way to sweet, scalloped flesh underneath. This time, the garlic is just right, humming in a butter sauce you'll be flagging down extra sourdough ($7) for. A few clams are strewn across the plate, seemingly for no other reason than "why not?"

The Rover doesn't make a lot of noise about sustainability. There isn't an agenda to showcase every part of the fish and dazzle guests with the untapped potential of carp liver. Staff are friendly and capable; the martinis are cold and dry. It's simply a pleasant little bistro and sometimes that's all a restaurant needs to be. Someone please open a Maine-style lobster shack next.

Vibe: British-channelling seafood bistro high on comfort

Go-to dish: Nick's fisherman's pie ($26)

Drinks: Solid list of natural-leaning wines, deliciously balanced cocktails, and belting collection of whiskies

Cost: About $130 for two, excluding drinks (and oysters)

This review was originally published in Good Weekend magazine