Classic Croque Monsieur

Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper. (5 minutes)

In a microwave-safe container, combine the milk and heavy cream. Microwave on high for about 90 seconds, or until warmed through but not boiling. (2 minutes)

In a medium saucepan, melt 3 tablespoons of butter over medium heat. Add the flour and whisk constantly until a smooth paste forms (a roux). Cook, stirring continuously, for about 2 minutes, until the roux is lightly golden and fragrant. (5 minutes)

Gradually whisk in the warm milk and cream mixture, ensuring no lumps form. Continue whisking until the sauce thickens and comes to a simmer, about 3-5 minutes. Reduce heat to low and cook, stirring constantly, for another 2-3 minutes to ensure the sauce is smooth and fully thickened. (10 minutes)

Remove from heat and season the Bechamel sauce with salt, pepper, and a pinch of nutmeg. Set aside. (2 minutes)

Melt the remaining 1 tablespoon of butter in a large skillet over medium heat. Brown 4 slices of bread on one side for about 2-3 minutes per side, until golden. (8 minutes)

Place the browned bread slices on the prepared baking sheet, browned side down. Spread each slice generously with the prepared Bechamel sauce. (5 minutes)

Top each slice with 2 slices of ham, followed by 1/2 cup of grated Gruyere cheese. Place the remaining bread slices on top, forming sandwiches. (5 minutes)

Spread the tops of the sandwiches with another generous layer of Bechamel sauce. Sprinkle each sandwich with 2 tablespoons of grated Gruyere and 2 tablespoons of grated Parmesan cheese. (5 minutes)

Bake in the preheated oven for 5-7 minutes, or until the cheese is melted and bubbly. (7 minutes)

Turn on the oven's broiler. Move the baking sheet about 6 inches from the heat source and broil the sandwiches for 2-3 minutes, or until the tops are golden brown and the cheese is bubbling. Watch carefully to prevent burning. (3 minutes)

Let the sandwiches cool slightly before slicing in half and serving warm. Garnish with cornichons, if desired.