Preheat oven to 350°F.
Melt butter in a large saucepan over medium-high heat. Sprinkle flour over the melted butter and whisk together. Cook for 1-2 minutes to make a roux and remove the raw flour taste until bubbly.
4 Tablespoons salted butter, 4 Tablespoons all-purpose flour
Whisk in salt, garlic powder, smoked paprika, and pepper.
½ teaspoon kosher salt, ½ teaspoon garlic powder, ½ teaspoon smoked paprika, ¼ teaspoon black pepper
Whisk in milk, broth, and dijon mustard. Continue to cook, whisking or stirring frequently, until thickened, about 3-5 minutes.
2 cups milk, 1 cup chicken broth, 1 Tablespoon dijon mustard
Whisk in the cheese, a handful at a time, until melted. Remove from the heat and stir in sour cream.
½ pound Swiss cheese, 1 cup sour cream
Combine shredded chicken and ham in a large bowl. Add cooked sauce and toss to coat evenly. Transfer the mixture to a 9x13-inch baking dish.
5-6 cups cooked rotisserie chicken, ½ pound black forest ham
In a separate bowl, combine Panko breadcrumbs, Shake'N'Bake seasoning packet, and Parmesan cheese. Drizzle with the melted butter and toss to coat. Sprinkle the seasoned breadcrumbs over the casserole dish.
2 Tablespoons salted butter, 1¼ cups Panko breadcrumbs, 1 envelope Original Shake'N'Bake chicken seasoning mix, ¼ cup powdered Parmesan cheese
Bake for 25-30 minutes until bubbly and hot and the breadcrumb topping is golden brown. Serve with cooked pasta or rice.