Can you work out the mystery behind Khéma’s incredible Steak-frites Café de Paris?

Khéma La Poste threw open the doors on its grand opening last month, boasting a bright new look, an energised team, and a bolder, wider menu than before. Not everything has changed though. Long-loved favourites from Khéma Pasteur are still there, especially the things we’re best at, alongside a delicious selection of new ideas and inspirations from around the world. But our heart rests in France, which is why the mysterious and magic Steak-frites Café de Paris is our banner dish.

Order it and on an elegant hot salver you’ll be served a deliciously rich and juicy grilled steak balanced out by the buttery and deep-mineral flavours of the Café de Paris sauce, accompanied with a generous serving of golden house-made French fries. Steak-frites Café de Paris embodies France’s earthier approach to food, with an emphasis on deep flavours, pots of butter and, of course, that predilection for a certain je ne sais quoi.

Because Café de Paris sauce is technically a mystery, which could be awkward when, as Auguste Escoffier notes, sauces are the very source of much of what we know as French cuisine. That said, Café de Paris sauce actually first came to prominence in Geneva (and we admit that fries come from Belgium, but still), where it was the speciality at the Café de Paris restaurant. Indeed, it still is their speciality, as well as at several other restaurants to whom it sells its secret formula under a strict licence.

However, a French restaurant group has also found fame with their version of Entrecôte Café de Paris, which is so renowned that when the New York Times went to Paris to talk steak, the resulting article starts with its restaurant, Le Relais de Venise, set in an elegant building in west-central Paris (and now also in London, New York and Mexico City).

Le Relais de Venise offers its guests a choice of one starter, one main and 20 desserts, and has done so successfully for more than 50 years. You can’t make a booking, yet people will line up around the block for the chance of a table. When The Independent newspaper visited the restaurant in 2003, they were as thrilled by the fact that the only choice one can make in relation to the main course is ‘rare’, ‘medium-rare’ or ‘medium’, as they were by the restaurant’s ability to make French people queue, in an orderly fashion. Appraising (and harshly judging) international queueing formations is a passionately pursued English past-time; some suspect it’s the only reason they ever travel.

Taking a stab at the ingredients of this divine mysterious sauce, renowned New York Times food writer Mark Bittman thought tarragon and shallots might be involved before he ran out of steam. Le Monde took a closer look when it published an ‘exposé’ in 2007 purporting to strip the mystery bare after subjecting the sauce to chemical analysis. The conclusion: chicken livers, fresh thyme and thyme flowers, full cream, white Dijon mustard, butter, water, salt, and pepper. One can almost imagine them secreting samples of the sauce out of the restaurant, James Bond-style. However their endeavours and their insolence were politely dismissed by the restaurant’s owner, Hélène Godillot, as so much nonsense.

And so a mystery it remains. And thus will Khéma’s own Café de Paris sauce remain a mystery too. You’ll simply have to come and try it to see if you can work it out.