Croque-Bleu

A blue cheese will not behave the way a croque-monsieur expects its cheese to behave. Gruyere and Comte melt into long even sheets and pull a stack of ingredients 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. So the croque-bleu is not a croque-monsieur with one ingredient changed. It is the same broiled, sauced, enclosed ham-and-cheese rebuilt around a cheese that overpowers everything unless something holds it down, and the thing that holds it down is the white sauce.

That reversal is the whole interest of the dish. In the parent sandwich the bechamel exists to keep a mild thing from drying out. Here it exists to keep a fierce thing from taking over. A blue laid straight onto toast with ham would read as a salt lick and nothing else; folded into a loose bechamel, the same cheese spreads its sharpness across a mild buttery base and lands as savour instead of assault. The sauce is run a little thinner and seasoned barely at all, because the cheese brings the salt for both. The ham is chosen for meekness, a pale poached jambon de Paris, so it gives body and a gentle cured note and then gets out of the way.

Every part of it fails in a way the plain croque does not. Too much blue and the sandwich is inedible, a single screaming note that buries bread, ham, and sauce together, which is why the cheese goes in by the spoonful and not the slab. A bechamel seasoned out of habit turns the whole thing brackish, since the Roquefort has already salted it twice over. Push the broiler too hard and the blue's fat splits and slicks the top instead of browning it, because a paste this rich greases before it gratines. And the soft sandwich loaf, fine under a tidy gruyere melt, sogs through under a wet weeping blue unless it is toasted firm first and built the moment it comes off the heat.

It reaches the table too hot to lift, the way its parent does, but it announces itself earlier. The smell hits first and it is unmistakable, the sharp barnyard ammonia of the blue cutting 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 gruyere croque. Cut in with the knife and the inside is molten and streaked grey-green, the bechamel and the blue reading as one tangy substance, the ham a quiet salt underneath. The first forkful stings high and peppery at the back of the palate, then the cream of the sauce arrives a beat later and pulls 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. A bistro in cheese country pours a glass of the local red beside it, or in the southwest a small pour of sweet Sauternes, the same wine a Roquefort cellar reaches for against the cheese, the sweetness doing to the wine what the bechamel does to the sandwich. It is unhurried sit-down food, taken slowly with cutlery, the most casual possible use of one of France's most serious cheeses.

Its near relations are the other named croques, and the line between them runs entirely through the cheese. The croque-auvergnat reaches for the firmer Bleu d'Auvergne or a slab of Cantal and eats heavier and earthier; the croque-savoyard takes washed-rind reblochon and turns soft and gentle; a croque-roquefort is simply the croque-bleu insisting on the one specific blue. What it is not is the cold blue-cheese-on-rye plate the Massif Central eats by the gram off a market board, a wedge of Bleu d'Auvergne with walnuts and honey in a sturdy loaf, which keeps the cheese raw and the bread unbroiled and asks none of the melting and buffering this one is built around.

The Cheese Is Older Than the Sandwich

The croque-bleu has no inventor and no first date, and chasing one is the wrong errand; it is a regional swap on a sandwich that itself only half-remembers its own beginning. The croque-monsieur it is built on appears in print in a Paris sporting paper in 1891 and turns up in Proust by 1919, which already places the parent format well before any of its cheese-named offshoots were being chalked onto slates. The blue version is a later cook's improvisation on that frame, 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 in 1411, confirming a practice the charter itself calls immemorial. The blue veining comes from Penicillium roqueforti, the mould native to the caves, and the cool damp air drawn through natural rock faults called fleurines; each wheel is pierced some forty times so that 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 whole 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 bechamel keeps no date of its own; the cheese at its centre has been a protected name since the year Charles VI was still on the throne, and a French legal protected one since 1925.