Preheat the oven to 375°F. Prepare a 9×13-inch baking dish by spraying it with cooking spray and set it aside.
Make the sauce in a dutch oven or large pot by first melting 1/2 cup (1 stick) unsalted butter over medium heat.
Once the butter is melted, whisk in 1/4 cup all-purpose flour, 1 Tablespoon garlic powder, 1/2 Tablespoon onion powder and 1 teaspoon black pepper. Once it is whisked together, continue to cook for 1 minute, stirring occasionally.
Continuously whisk in 1 1/2 cups whole milk to avoid any lumps. Continue with 1/2 cup chicken stock, followed by 1/2 cup heavy cream.
Stir in 3 Tablespoons dijon mustard.
Lastly, add 8 ounces shredded swiss cheese and stir to combine and melt. Take off the heat.
Stir in 16 ounces penne pasta, cooked and drained well until coated in the sauce.
Add 3 cups cooked shredded chicken and 1 1/2 cups small diced ham, stir to combine.
Add the mixture to the prepared baking dish.
Top evenly with 8 ounces shredded swiss cheese.
In a medium sized bowl, stir together 1 1/2 cups panko breadcrumbs and 3 Tablespoons unsalted butter, melted.
Sprinkle this evenly all over the top of the casserole.
Bake uncovered for 25-30 minutes until bubbly along the edges and the breadcrumbs are browned. If topping starts to get darker than you would like, cover with aluminum foil and continue baking.
Serve immediately topped with dried parsley, if desired and enjoy!
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Notes
Please refer to my FAQ’s (Frequently Asked Questions) and ingredient list above for other substitutions or for the answers to the most common questions.
One 8 ounce package of shredded Swiss cheese is equal to about 2 cups smeasured. Keep in mind, cheese isn't measured in liquid volume, it's measured in weight volume so 8 ounces of shredded cheese is NOT one cup like it would be if you were measuring a liquid - it would be about 2 cups.