Croque Madame
Chapter 2 — The Mains
If you have ever sat at a white-papered table in SoHo, torn into a Croque Madame, and wondered how a simple ham and cheese sandwich could taste so profoundly rich, the secret lies in unapologetic technique. The bistro version does not cut corners. It requires real, high-fat cultured French butter, aged Gruyère that you grate yourself, and a proper Sauce Mornay that must be stirred patiently. This is a knife-and-fork sandwich. The bread is crisped in a cast-iron skillet, smothered in velvety sauce, baked until molten, and crowned with an egg fried so gently that the yolk remains a liquid gold sauce. Yes, it is an endeavor. Yes, this is exactly what Spring Street tastes like.
Before you start
Warm the milk gently before beginning the Sauce Mornay.
Introducing cold milk to a hot roux increases the likelihood of a lumpy, broken sauce.
Grate all of the Gruyère fresh from a block.
This guarantees the long, elastic strings of cheese characteristic of a perfect croque and ensures a seamless emulsion in your sauce.
Ingredients
- cultured French butter6 tbsp
- all-purpose flour2 tbsp
- whole milk1 1/4 cup
- large egg yolk1 large
- imported Gruyère or Comté cheese2 cup
- Dijon mustard4 tsp
- nutmeg1 pinch
- kosher salt1 pinch
- white pepper1 pinch
- pain de mie or brioche4 large
- Jambon de Paris or mild deli ham8 oz
- large farm eggs2 large
- fleur de sel1 pinch
- black pepper1 pinch
- fresh chives1 tbsp
Method
- 01
Melt 2 tablespoons of the butter for the Mornay over medium-low heat until foaming, then whisk in the flour to create a pale roux.
Cook the paste for 1 to 2 minutes, whisking constantly until it yields a pale, nutty aroma, ensuring it takes on absolutely no brown color.
- 02
Slowly stream the warmed whole milk into the roux while whisking vigorously to prevent lumps.
Once incorporated, bring the sauce just to a bubble, then immediately drop the heat to the lowest simmer and cook for 5 to 7 minutes until glossy and thick enough to heavily coat the back of a spoon.
- 03
Remove the saucepan entirely from the heat to temper the egg yolk and mount the cheese.
Whisk in the egg yolk immediately to prevent scrambling, followed by a half cup of the grated Gruyère, 1 teaspoon of Dijon mustard, nutmeg, salt, and white pepper, stirring until perfectly smooth.
- 04
Heat a large cast-iron skillet over medium heat and toast the buttered interior sides of the bread until deeply golden.
Lightly butter one side of all four slices of bread using 3 tablespoons of softened butter, placing them butter-side down in the skillet for 2 to 3 minutes to create a structural barrier against the wet sauce.
- 05
Assemble the sandwiches on a parchment-lined baking sheet by layering the remaining mustard, folded ham, and a half cup of Gruyère between the toasted faces.
Place the top slice of bread toasted-side up, which protects the structural integrity of the crumb when you apply the sauce.
- 06
Ladle the warm Mornay heavily over the tops of the sandwiches, spreading it to the very edges, and pile high with the remaining grated Gruyère.
The sauce should be thick enough that it does not immediately run off the sides, but generous enough to feel luxurious.
- 07
Broil the sandwiches for 3 to 5 minutes until the cheese is violently bubbling and deeply caramelized with dark leopard spots.
Watch it like a hawk under intense direct heat, then remove from the oven and let rest for 2 minutes so the molten lava interior can slightly set.
- 08
Fry the eggs gently in the remaining tablespoon of butter over medium-low heat to achieve a set white and a gloriously liquid yolk.
Crack the eggs into the skillet and cook for 3 to 4 minutes without developing tough, crispy brown edges, basting the whites slightly with melted butter if necessary.
- 09
Crown each sandwich with a perfectly fried egg, season with fleur de sel, and garnish with minced chives.
Transfer the sandwiches to warmed plates using a wide spatula, gently slide the egg onto the center, and serve immediately with a heavy steak knife.
Notes
The Sauce Mornay fundamentally benefits from being made a day in advance.
Chilling it overnight allows the starches to fully hydrate and the flavors to meld. When ready to assemble on a weeknight, simply warm the set Mornay over low heat, whisking in a splash of heavy cream to restore its velvety, pourable texture.
Do not substitute generic American Swiss cheese or pre-shredded varieties.
Pre-shredded cheeses are coated in anti-caking agents that yield a grainy, broken sauce, while generic Swiss lacks the complex, nutty depth and proper melting profile of a true cave-aged Gruyère or Comté.