Croque-Bleu

A blue cheese will not behave the way a croque-monsieur expects its cheese to behave. Gruyere and Comté melt into long even sheets that pull a stack together; Roquefort, crumbled in, breaks into soft salty pockets that slump and weep rather than flow, and it arrives carrying three or four times the punch of an Alpine slice. The whole build then changes to keep that punch in check. The same broiled, sauced, enclosed ham-and-cheese gets rebuilt around a cheese that would otherwise read as a salt lick and nothing else, and the thing that reins it in is the white sauce.

In the parent sandwich the béchamel keeps a mild thing from drying out; here it does the opposite job, spreading a fierce cheese's sharpness across a mild buttery base so it lands as savour instead of assault. French kitchen practice is specific about how. The blue goes into the béchamel off the heat, at room temperature, and only enough is stirred in to soften, not dissolve, so it streaks the sauce rather than vanishing into it. The sauce itself is left nearly unsalted, because the Roquefort has already salted it twice over, and a common brasserie hedge cuts the blue half-and-half with grated gruyère, buying meltability and dialling the salt back down. The ham is chosen for meekness, a pale poached jambon de Paris that gives body and a gentle cured note and then steps aside.

The detail that sets this croque apart from every other named one is what gets added to sweeten it. A blue-cheese croque on a brasserie slate is far more likely than its siblings to arrive carrying thin slices of pear, sometimes a tart apple, and a scatter of crushed walnuts pressed inside before it goes under the broiler. That trio is not a chef's whim. It is the Roquefort cheeseboard, the standing French pairing of the blue with walnuts, honey and something sweet, folded bodily into a hot sandwich, the fruit doing across the bite what the béchamel does within it. No croque-savoyard or croque-auvergnat reaches for fruit; this is the one that does, because this is the one built on the cheese that the pear was always meant to meet.

It reaches the table too hot to lift, the way its parent does, but it announces itself earlier. The sharp barnyard ammonia of the blue cuts through the toasted-bread warmth before the plate is even down. The top is blistered and patchy gold where the sauce caught rather than the smooth burnish of a gruyère croque, and a wet weeping blue will sog a soft loaf through unless the bread is toasted firm first and the thing built the moment it leaves the heat. Cut in, and the inside is molten and streaked grey-green, the béchamel and the blue reading as one tangy substance over the quiet salt of the ham. The first forkful stings high and peppery against the soft palate, and only then does the cream of the sauce arrive a beat later to pull it back from the edge.

It lives on bistro and brasserie slates rather than in any codified canon, written up beside the croque-monsieur and the croque-madame as the sharp one, the order a regular makes when the standard ham-and-cheese feels too tame. In cheese country the glass beside it is the local red; in the southwest it is a small pour of sweet Sauternes, the wine a Roquefort cellar reaches for against the cheese, the sweetness doing to the wine what the pear and the béchamel do to the sandwich. It stays unhurried sit-down food taken with cutlery, the most casual possible use of one of France's most serious cheeses.

The Cheese Is Older Than the Sandwich

The croque-bleu carries no named inventor and no founding date; it is a later cook's improvisation on a frame that itself only half-remembers its own beginning. The croque-monsieur appears in print in the Paris sporting paper La Revue Athlétique on the twenty-fifth of September, 1891, describing a hot ham sandwich met on a boating trip in England, and turns up in Proust by 1919, which places the parent format well before any of its cheese-named offshoots were chalked onto a slate. The blue version is undated and unattributed, the work of someone with good cheese to hand and a broiler going.

The cheese, though, carries a record the sandwich never could. Roquefort, the ewe's-milk blue ripened in the limestone caves of the Combalou plateau above Roquefort-sur-Soulzon, is among the most documented foods in France. Charles VI granted the village a monopoly on ageing the cheese in those caves on the fourth of June, 1411, confirming a practice the charter itself calls immemorial. The veining comes from Penicillium roqueforti, the mould native to the caves, carried on cool damp air drawn through natural rock faults called fleurines; each wheel is pierced some forty times so the air can reach the spores and run the veins through the paste.

The legal record is just as exact. On the twenty-sixth of July, 1925, Roquefort became the first cheese in France to win a protected designation of origin, the founding case of the AOC system that now governs French food, its name reserved by law to wheels aged in the Combalou caves and nowhere else. The sandwich that melts it into a béchamel keeps no date of its own. The cheese at its centre has been a guarded name since Charles VI sat the throne, and a French legal one since 1925, longer than most things one is served for lunch.