You might not know it, but the oldest church in London is in the City.

St Bartholomew-the-Great in West Smithfield was founded in 1123 as an Augustinian monastery. It’s now a thriving church, and even hosts regular music performances, in case you need a lunch break with an extra topping of religious repose. While visiting the church, you may also spot a small Frenchman in the corner of the churchyard tending to its garden. This man is Pascal Aussignac, the legendary head chef and proprietor of Club Gascon.

The Michelin-starred restaurant has been a flagship for first-class French cooking for nearly 20 years. This year, for the first time in two decades, the venerable institution has undergone a complete refurbishment.

But Chef Pascal is not one to idly stand by while others are working. Instead, he convinced the powers-that-be to let him cultivate the little garden at the rear of the neighbouring churchyard. He used materials recycled from the restaurant, including wood from the former bar, to lay out the beds. And now he’s growing produce for use on the restaurant’s new menu.

This is a man who, even after all these years, still visits New Covent Garden Market every week to purchase fresh flowers and personally design the flower arrangements for his Gascon Connection restaurants in London. It’s this obsessive attention to detail that helps elevate his food to frankly ecclesiastical levels.

Every course is immaculately presented but without ever trying too hard

One of my banker friends is obsessed by Michelin. He challenged himself – and succeeded – in dining at every Michelin-starred restaurant in London in one year. His favourite of the lot? Club Gascon.

It was Aussignac’s masterful treatment of foie gras that really sealed the deal for him. And I’m happy to report the chef hasn’t lost his touch – or his supplier.

Much of the produce is sourced from the area he grew up in – Gascony (hence the name). This is a place where charcuterie, cassoulet, armagnac, and, er, ducks rule the roost.

As part of our autumn tasting menu, the Toulouse foie gras is masterfully paired with a sharp cranberry jus and sublime gingerbread canelé. This heady combination is lifted further by the wine; a Jurançon from Jean-Marc Grussaute of the small but remarkable Domaine Larredya.

Other carnivorous delights include a venison carpaccio ingeniously accompanied by sea urchin jus, as well as roasted grouse with a Guinness and oyster sauce that I’d happily have drunk on its own. Although, on balance, the silky Haut-Bergey 2004 was preferable. The scrambled brillat-savarin with sweet truffle honey and pistachio was a dish of beauty – the rich, creamy cheese enough to make a grown man weep (certainly once the gout kicks in, anyway.)

Every course is immaculately presented but without ever trying too hard. This is the sort of confidence that comes from winning a Michelin star for 15 years in a row.

Ostensibly, I went here to report on the renovations, which are, as you’d expect, rather nice. But when the food is this good, who really cares about the room anyway?

Club Gascon, 57 West Smithfield, EC1A 9DS; 020 7600 6144;