Balthazar opened on April 21, 1997, in a former textile warehouse at 80 Spring Street in SoHo. Keith McNally — who had already opened Odeon and Café Luxembourg — built a French brasserie interior from scratch: 180 seats across high-backed red leather banquettes, scarred brass mirrors that made the room look like it had been there for fifty years, high tin ceilings, and a zinc bar. The restaurant also has its own bakery at the same address, which supplies the bread and pastries and sells to the public before the kitchen opens each morning.
The croque monsieur is $23 on the breakfast menu, served with mixed greens. It is not a signature dish the way the French onion soup has been analyzed and replicated. It’s a brasserie standard — on every menu at every comparable restaurant in France. What makes the Balthazar version worth replicating is that it’s done with the ingredients and technique those standards actually require, rather than shortcuts most home recipes make without realizing.
Three Things Most Croque Monsieur Recipes Get Wrong
Only béchamel on top, none inside. A proper brasserie croque monsieur has béchamel in two places: inside the sandwich (about 2 tablespoons spooned over the ham before the top bread slice goes on) and thick on top before broiling (about 3 tablespoons per sandwich). Most home recipes — and most online versions — skip the internal layer entirely and only sauce the outside. The result is a toasted ham-and-cheese sandwich under a sauced crust, which is not the same thing. The inside béchamel is what coats every bite through the interior, makes the Gruyère inside melt into something cohesive, and creates the indulgent quality that defines the dish. Without it, the interior is dry.
American deli ham instead of jambon de Paris. Balthazar’s menu lists “French ham” — jambon de Paris, the mild, cooked-and-pressed white ham that has no smoke, no brine assertiveness, and very little salt. Its purpose in the sandwich is to add a layer of clean savory protein without competing with the Gruyère and béchamel. Black Forest ham turns the sandwich into a different dish. Honey ham is too sweet against the Dijon and Gruyère. Regular American deli ham is too briny. Jambon de Paris lets the sauce and cheese lead; everything else fights them.
Pre-shredded Gruyère. Anti-caking agents in bagged cheese prevent proper melting. Under the broiler, pre-shredded Gruyère stays grainy and melts pale and uneven. Hand-grated from a block, Gruyère melts smooth and caramelizes into a deeply golden, slightly crunchy, bubbling crust — which is the whole point of the top layer.
The Ham
Jambon de Paris is available at Whole Foods (deli section, often labeled “uncured ham” or “Paris-style ham”), at specialty food stores, and from French deli suppliers online. Boar’s Head makes a product called Deluxe Ham that is mild and unsmoked and works well as a substitute. Any high-quality mild cooked ham with no smoke and no sweetness works.
Two to three thin slices per sandwich is correct. More than that and the inside becomes assertively salty; the ham’s flavor will push through the béchamel and Gruyère rather than sitting quietly underneath them.
The Béchamel Is the Dish
Remove the béchamel from a croque monsieur and you have a toasted ham and cheese. The sauce is not a condiment; it is the structural element that defines what the dish is and separates it from a panino or a melt.
For a clean, nutty béchamel with no raw-flour taste: cook the roux — the butter-and-flour mixture — for 2 to 3 minutes before the milk goes in. Most home recipes call for 30 to 60 seconds; the longer cook time is what burns off the floury flatness and develops the faint nuttiness that makes the sauce taste like food rather than a thickener. The roux should smell slightly toasted, not raw.
Add the milk in a thin, steady stream while whisking — not all at once. All at once creates lumps that are difficult to whisk out; thin stream while whisking creates an emulsion that thickens evenly. Target thickness: the sauce should pull away from the pan edges when you draw the spatula across the bottom, and should hold its shape when spooned. If it’s runny, it will slide off the top of the sandwich before it can caramelize under the broiler. If it’s too thick, a splash of milk and another minute of stirring over medium heat will loosen it.
The Dijon goes in off the heat — whisked into the finished sauce, not stirred in while it’s still cooking. Cooking drives off the volatile compounds that give Dijon its sharpness; added off the heat, it retains its characteristic sting and keeps the sauce tasting like something.
Inside and Outside
Divide the finished béchamel into roughly two portions: a smaller one (about 4 tablespoons total, 2 per sandwich) that goes inside, and a larger one (about 6 tablespoons total, 3 per sandwich) that goes on top.
For the inside: spoon the smaller portion over the ham and Gruyère before the top slice of bread goes on. It doesn’t need to be hot; room-temperature béchamel applied inside will heat through completely in the oven. The application doesn’t need to be precise — spread it roughly across the ham surface with the back of a spoon.
For the outside: once the sandwiches are assembled and back on the sheet pan, spoon the remaining béchamel over the top surface of each, covering the entire face so no dry bread is showing. Cover the béchamel with hand-grated Gruyère, enough to form a layer. This is what goes under the broiler and caramelizes.
The Broiler Is the Finishing Step
Ten minutes at 400°F heats the sandwich through and starts crisping the bread edges. The broiler is what finishes the top — blistering the Gruyère into a caramelized, deeply golden crust with a few spots of brown.
Broil on high, rack in the upper third, and watch without moving. The window between properly caramelized and burnt is around 30 to 45 seconds at full broiler temperature. The signal to pull: the Gruyère is deeply golden across most of the surface with real spots of caramelized color, the béchamel visible at the edges is beginning to color, and the bread perimeter is visibly crisped. Pull the moment that combination is there.
The béchamel under the crust should still be soft — not dried out. The crust is the exterior; the sauce underneath remains yielding.
The Salad Alongside
A dressed green salad is not optional decoration. The bitterness of frisée and the acid of a sharp Dijon vinaigrette cut through the fat of the béchamel and Gruyère and make the second half of the sandwich taste as good as the first. Without it, the richness accumulates.
A two-minute Dijon vinaigrette: 1 tablespoon Dijon, 1 tablespoon white wine vinegar, 3 tablespoons olive oil, a pinch of salt, whisked together. Dress the greens just before the sandwiches come out of the oven. Cornichons on the side — four or five small ones — do the same job if you’d rather skip the salad: their brine and crunch are the natural foil for a fat-rich sandwich.
Scaling
This recipe makes 2 sandwiches. The béchamel scales directly: double every quantity for 4 sandwiches. Made-ahead béchamel (up to 3 days in the refrigerator, plastic wrap pressed directly on the surface) means the active work is 15 minutes from start to plate. The sandwiches must be assembled and broiled fresh — assembled sandwiches sitting in béchamel on a counter soften.
