In a medium saucepan, melt 3 tablespoons of butter over low heat. Gradually whisk in 3 tablespoons of flour to create a roux, cooking it for about 2 minutes until it turns a light golden color.

Slowly pour in 1 cup of milk, stirring constantly to eliminate lumps. Once the sauce thickens and coats the back of a spoon, mix in a pinch of nutmeg and salt to taste.

Lay out two slices of your favorite bread on a clean surface. Spread a layer of béchamel sauce on each slice.

On one slice, layer 2-3 slices of ham followed by a handful of shredded gruyère cheese. Top with the second slice of bread, béchamel side down.

Heat a non-stick skillet over medium heat and add 1 tablespoon of butter. Cook the sandwich for about 3-4 minutes until golden brown.

Flip the sandwich, adding another tablespoon of butter, and cook for an additional 3-4 minutes until both sides are crisp and golden.

For an extra touch, preheat the broiler. Once both sides are browned, transfer the sandwich to a baking sheet and broil for 1-2 minutes.

Remove from the oven, cut in half, and serve immediately.