01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with butter or non-stick spray.
02 - If using regular lasagna noodles, cook according to package directions until al dente. Drain and lay flat on a clean surface to prevent sticking.
03 - In a medium saucepan over medium heat, melt the butter. Whisk in the flour and cook for 1 to 2 minutes to form a roux.
04 - Gradually whisk in the whole milk, stirring constantly until the sauce thickens, about 5 minutes.
05 - Stir in the Dijon mustard, garlic powder, onion powder, salt, and black pepper. Remove from heat and set aside.
06 - Spread a thin layer of béchamel sauce across the bottom of the prepared baking dish. Arrange a single layer of noodles over the sauce.
07 - Top the noodles with half the chicken, half the ham, and one-third of the Swiss cheese. Spoon additional béchamel sauce evenly over the layer.
08 - Add another layer of noodles, followed by the remaining chicken, remaining ham, another third of the Swiss cheese, and more sauce.
09 - Finish with a last layer of noodles, the remaining béchamel sauce, all the mozzarella, and the Parmesan cheese sprinkled on top.
10 - Cover the dish tightly with aluminum foil and bake for 30 minutes.
11 - Remove the foil and continue baking for 15 to 20 minutes until the cheese is golden and the edges are bubbly.
12 - Let the lasagna rest for 10 minutes before slicing to allow the layers to set. Garnish with chopped fresh parsley if desired.