Start by melting 3 tablespoons of unsalted butter in a saucepan over medium heat. Once the butter has melted, whisk in the flour. Stir it continuously for about two minutes—it should look bubbly but not brown. Slowly pour in the warmed whole milk while keeping a steady whisk. Cook until the sauce thickens. Add in the salt, pepper, whole-grain mustard, Dijon mustard, and smoked paprika. Stir frequently until it’s silky and thickened, then set it aside.

Preheat your oven to 400°F (200°C). While it heats up, spread softened butter on one side of your bread slices. Place them butter-side down on a baking sheet. Toast in the oven for about 5-6 minutes or until golden brown. This will create a lovely crunchy base for your toppings.

Once your bread is toasted, let’s get assembling! Spoon a generous layer of béchamel sauce over each slice. Be sure to cover every corner; we don’t want any dry bites here.

Now, layer the thick-cut ham on top of the béchamel. Don’t hold back—get a good amount on there. Next, take the Gruyère cheese and generously sprinkle it over the ham. Follow this with a sprinkling of Parmigiano-Reggiano cheese. Trust me; you want that cheesy crust!

Slide the baking sheet into the oven and let it bake for about 10-12 minutes. You’re looking for that delightful golden-brown crust. If you like it extra crispy, feel free to broil it for a minute or two at the end—but keep a watchful eye!