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 set aside on a clean towel.
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 light roux.
04 - Gradually whisk in the milk, stirring constantly, until the sauce thickens and coats the back of a spoon, about 5 minutes. Stir in Dijon mustard, garlic powder, onion powder, salt, and pepper. Remove from heat.
05 - Spread a thin layer of béchamel sauce across the bottom of the prepared baking dish. Arrange a layer of noodles over the sauce, then top with half the chicken, half the ham, and one-third of the Swiss cheese. Spoon additional sauce over the cheese.
06 - Repeat the layering: noodles, remaining chicken, remaining ham, another third of the Swiss cheese, and more sauce.
07 - Finish with a final layer of noodles, the remaining béchamel sauce, all the mozzarella, and the Parmesan cheese.
08 - Cover the dish tightly with aluminum foil and bake for 30 minutes.
09 - Remove the foil and continue baking for 15 to 20 minutes until the top is golden brown and bubbling.
10 - Let the lasagna rest for 10 minutes before slicing to allow the layers to set. Garnish with chopped fresh parsley if desired.