Want to give the finger to every low-carb, low-fat, low-salt doomsday dietary edict in the most delicious way?

Take a potato that’s steamed, mashed, formed into a long rectangle, then fried crisp. Top with thick slices of housemade sea-bream bottarga for a hit of salty pleasure and surround with a moat of chive-flecked butter sauce. Surf that dopamine rush with a smug smile.

It’s the snack that brings sexy back to late-night sipping and supping. Meaning ‘underneath’ or ‘below’ in French, Dessous is the subterranean bar yang to the day-through-night ying of bistro Hazel above – the handsome new double act that’s taken over three levels of the T&G Building on Flinders Lane.

Shaking and stirring until 1am, it’s already a hospo hotspot. They come for Hop Nation American red and negronis and skin-contact sauv blanc, but also a feed – that potato number is just one of the must-orders chef Dan Sawansak (late of Higher Ground and MoVida) is turning out of the open kitchen.

Whether a fried-to-order doughnut stuffed with spanner crab and corn custard, the fluffy comfort of a pork katsu sando with sweet bulldog sauce or a knockout bowl of larb-spiced pork meatballs with toasted rice and a splash of fish sauce there are many good things to go with the good booze on offer.

To wit: the poshest wedges in town with ’njuda sour cream, braised fennel and sheaths of crunchy-fried chicken skin, while a tranche of skate teamed with hazelnuts, grapes and jamón is one of the fish dishes of the year.

The cellar of 120-odd wines is filled with thinking drinking with a Eurocentric air, and almost two dozen of them are poured by the glass at the table.

Service is sharp and switched on, the cutlery hefty, the napkins linen, the stemware as elegant and refined as the playlist is eclectically cool.

Underneath but a cut above – for delicious, dangerous, late-night good times Dessous gets two thumbs up.