The most famous dish at Paris’ Maison Rostang, a two-Michelin-star restaurant run by iconic Parisian chef Michel Rostang, is the black truffle sandwich — two slices of farmhouse bread, a generous slathering of salted French butter and a thin layer of black Perigord truffles. It costs 98 euros, making it one of the more expensive sandwiches in the world, according to those who keep track of such things.

At Madame Monsieur, a tiny French sandwich shop and café in downtown Los Angeles that opened about a year ago, you can have what is essentially the same sandwich — cooked by a woman who spent a few months training in Rostang’s kitchen — for the relative bargain price of $25. It even comes with an arugula salad, tossed in Dijon vinaigrette, on the side.

The off-menu “Le Truffle” sandwich, as it's called at Madame Monsieur, is made from two slices of sourdough from local baker Clark Street Bread, a near-indecent amount of Rodolphe le Meunier’s salted beurre de baratte (a luxuriant cultured butter from Normandy that’s probably the best butter available in the United States) and a layer of fresh black winter truffles imported from Périgord, France. And yes, the sandwich is as intoxicating and indulgent as you might expect — imagine the heady, rich aroma of the world’s greatest garlic bread amped up to the 10th power.

Does all this seem utterly ridiculous? If you think so, it would be hard to persuade you otherwise. But it might be helpful to back up a minute: Madame Monsieur is the brainchild of Alison Barber, a former French fashion model turned chef, and her husband, Kerian Jarry, a furniture designer for Knibb Design who arrived in the United States about three years ago. Jarry’s mother, Sophie Clerico, who is also the ex-wife of French actor Anthony Delon, helps operate the shop. The entire family — which is already about as French as it gets — grew up around the Parisian cabaret business. Jarry’s grandfather was involved in running one of the city’s more infamous cabaret houses. To them, Paris holds memories of walking the streets with a tiny, wax-wrapped croque-monsieur, and they had a hard time finding a satisfying equivalent in Los Angeles.

So the family opened Madame Monsieur near Sixth and Hill, specializing in the croque-monsieur, a traditional French sandwich that’s made with thin slices of jambon de Paris, Gruyère cheese, crème fraiche and Dijon mustard, then toasted with a blowtorch until it’s crisp and bubbly. There are other toasty sandwiches on the menu, made with smoked salmon, egg salad or tuna. The humble jambon-beurre, served on Clark Street Bread and stuffed simply, with French ham and beurre de baratte, is easily one of the best versions in town — a spectacular little ode to bread-butter-meat. On any given day, you might find office workers crowding into the shop, ordering toasted sandwiches, cups of warm tomato soup, slices of quiche and gooey, caramel-filled canelé (baked by a local French pâtissier).

But back to that truffle sandwich. Barber learned the technique for making it during an internship with Rostang, who later gave the family his blessing to serve their own version in L.A. Only a few are made each day at the café (the secret: The butter needs 24 hours to infuse with the truffles), and once the sandwiches are sold out, there's no replenishing them until the next day. Customers can call and reserve a sandwich, but Madame Monsieur asks that they pay in advance with a credit card. And since winter truffle season lasts only until mid-March, the sandwich has but a few weeks left this season.

Madame Monsieur, 512 W. Sixth St., downtown; (213) 239-9440,

LA Weekly