# Required Ingredients:
→ Potatoes & Ham
01 - 3 lbs russet potatoes, peeled and thinly sliced
02 - 3 cups cooked ham, diced
→ Sauce
03 - 6 tablespoons unsalted butter
04 - 1 large yellow onion, finely chopped
05 - 4 cloves garlic, minced
06 - 1/3 cup all-purpose flour
07 - 3 cups whole milk
08 - 1 cup heavy cream
09 - 2 teaspoons Dijon mustard
10 - 1 teaspoon kosher salt
11 - 1/2 teaspoon black pepper
12 - 1/2 teaspoon paprika
13 - 2 cups sharp cheddar cheese, shredded
14 - 1 cup Gruyère cheese, shredded
→ Topping
15 - 1 cup shredded cheddar cheese
16 - 1/2 cup panko breadcrumbs (optional)
17 - 2 tablespoons unsalted butter, melted (for panko)
# How-To Steps:
01 - Preheat oven to 375°F and grease a deep 9x13-inch baking dish.
02 - Melt butter in a large skillet over medium heat. Add chopped onion and cook until softened, approximately 4 to 5 minutes. Add garlic and sauté for 1 additional minute.
03 - Whisk in flour and cook for 1 to 2 minutes until lightly golden, stirring constantly.
04 - Gradually whisk in whole milk and heavy cream. Stir in Dijon mustard, kosher salt, black pepper, and paprika. Continue whisking until the sauce thickens and is smooth, about 5 minutes.
05 - Remove sauce from heat and stir in sharp cheddar and Gruyère cheeses until fully melted and smooth.
06 - Spread half of the sliced potatoes evenly in the baking dish, followed by half of the diced ham. Pour half of the cheese sauce over the layers. Repeat with remaining potatoes, ham, and sauce.
07 - Sprinkle extra shredded cheddar cheese evenly over the top. If using, toss panko breadcrumbs with melted butter and scatter over the casserole.
08 - Cover dish with aluminum foil and bake for 50 minutes.
09 - Remove foil and continue baking for an additional 20 to 25 minutes until potatoes are tender and the top is golden and bubbly.
10 - Allow casserole to rest for 10 to 15 minutes before serving to set.
