A croque without béchamel is just a toasted ham-and-cheese sandwich. The sauce — spooned thickly over the top before broiling — is what makes it a croque, and Buvette’s version is specifically different from a standard bistro béchamel in two ways.

First: both Dijon and whole-grain mustard are whisked into the finished sauce, not just spread on the bread inside. This distributes the mustard flavor throughout the entire topping layer, not only at the interior contact point. The béchamel tastes like something — sharp, slightly pungent, specifically French — rather than just rich and creamy. Second: the roux is cooked for 3 to 4 minutes before the milk goes in, which is longer than most béchamel recipes call for. That extra cook time eliminates the raw-flour taste that makes standard béchamel taste flat or pasty.

The thickness matters too. Jody Williams’ ratio — 1.5 tablespoons of butter, 2 tablespoons of flour, only 3/4 cup of milk — produces a sauce thick enough to sit on the bread while it bakes instead of running down the sides. The target is pudding consistency: the sauce should pull away from the pan edges when it’s ready and hold its shape when spooned. If it’s thin, keep stirring over medium heat until it thickens.

Most croque madame recipes call for jambon de Paris — mild French cooked ham — and that is the classic. Buvette uses prosciutto. This is a meaningful difference: prosciutto is fattier, saltier, and more complex than boiled ham. Its fat renders slightly under the heat of the oven, seasoning the inside of the sandwich from the inside. The salt level is higher, which the sweetness of the béchamel balances against. Its dry-cured texture holds up better against the mustard and bread than watery cooked ham.

Two thin slices per sandwich is right. More than that and the inside becomes assertively salty; less and the prosciutto gets lost. If you want to stay with jambon de Paris or a high-quality mild cooked ham, the sandwich is still good — the flavor is milder and more neutral, which is a valid choice if you want the béchamel to lead. Avoid smoked ham (too much competition with the mustard) and honey ham (too sweet against Gruyère).

Buvette finishes the top of each sandwich with Gruyère mixed with finely grated Parmesan, then a small pinch of herbes de Provence before it goes in the oven. These are small details, but they matter.

The Parmesan adds a nutty, crystalline quality that Gruyère alone doesn’t have — when it caramelizes under the broiler, it forms a slightly crispier, more deeply flavored crust than straight Gruyère. The herbes de Provence (thyme, rosemary, oregano, savory) is the detail most home copies miss. The quantity is tiny — a pinch per sandwich — but it’s what makes the finished crust taste like something you’d get in a French bistro rather than just melted cheese. McCormick sells it at most grocery stores.

Grate the cheeses yourself. Pre-shredded Gruyère has anti-caking agents that prevent proper melting; the crust stays grainy. A box grater for the bulk of the Gruyère, and a fine Microplane for the Parmesan so it distributes evenly and melts into the Gruyère layer during broiling.

You cannot replicate the top of a Buvette croque madame in a pan or at standard oven temperature. The broiler is what blisters the béchamel and cheese into a deeply golden, caramelized crust — spotted dark brown in places, still slightly soft and yielding in others. That combination of textures is the whole point of the top layer.

Rack in the upper third, broil on high, and watch it the whole time. The difference between perfectly blistered and burnt is under a minute at full broiler temperature. The signal to pull: real spots of dark brown on the Parmesan, the Gruyère bubbling and caramelized at the edges, the bread crisping visibly around the perimeter. The béchamel under the crust should still be soft and yielding — not dried out.

Jody Williams describes the egg as resting “like a good hat, leaning just so.” It’s over-easy — flipped once, briefly, so the very top of the white is set while the yolk stays liquid. The distinction from sunny side up: the top surface of the white is cooked through instead of translucent and slightly gelatinous, which gives the egg more structural stability on top of the hot sandwich. The yolk is still fully liquid either way; that’s the point.

Cook it in butter over medium-low heat. The moment the white is fully set underneath, flip once and cook for exactly 10 seconds — enough for the top of the white, not enough to start cooking the yolk. Slide onto a plate to rest while the sandwiches come out from the broiler. Place it on the sandwich immediately before serving; the egg and the béchamel should be at the same temperature when you eat.

At Buvette, the croque madame comes with dressed greens — frisée or mâche in a sharp vinaigrette — and the salad is not decorative. The bitterness of frisée and the acid of the vinaigrette cut through the fat of the béchamel and egg yolk, cleaning the palate between bites and making the second half of the sandwich taste as good as the first.

A simple Dijon vinaigrette takes two minutes: 1 tablespoon Dijon, 1 tablespoon lemon juice or white wine vinegar, 3 tablespoons olive oil, a pinch of salt, whisked together. The insalata verde served a few blocks away at Via Carota — Jody Williams’ other West Village restaurant — is the model here: cold, crisp greens in a sharp, mustard-forward dressing, nothing more. If you’d rather skip the salad, cornichons on the side serve the same purpose — the brine and crunch are a natural foil for the richness.

The béchamel keeps for 3 days in the refrigerator, covered with plastic pressed directly on the surface to prevent a skin. Reheat over low heat with a splash of milk, stirring, before using. The sandwiches themselves should be assembled and broiled fresh — bread that sits assembled softens. With the béchamel pre-made, the active work is 15 minutes from start to plate: toast, build, broil, fry, serve.

To make croque monsieur instead of madame: follow the recipe exactly and stop before the egg step. Everything else — the béchamel, the prosciutto, the Parmesan-Gruyère crust, the herbes de Provence — is identical. The monsieur is lighter and faster; the madame is the Buvette dish.