First, I melt butter in a saucepan over medium heat and whisk in flour for a few minutes. Gradually adding warm milk while stirring prevents lumps. Then, I season with salt, pepper, mustard, and nutmeg for that classic French flavor.
I spread a generous layer of béchamel on each bread slice, then add ham and a sprinkle of Gruyere. Topping with the remaining bread, béchamel side up, ensures every bite is creamy.
Next, I sprinkle Parmesan and more Gruyere on top. Baking at 425°F for about 10–15 minutes until golden and bubbly always makes me smile—the smell alone is irresistible.