01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with butter or nonstick spray.
02 - If using regular lasagna noodles, cook them according to package directions until al dente. Drain and set aside. Skip this step if using no-boil noodles.
03 - In a medium saucepan over medium heat, melt the butter. Whisk in the flour and cook for 1 to 2 minutes, stirring constantly to form a smooth roux.
04 - Gradually whisk in the whole milk, stirring constantly to prevent lumps. Continue cooking until the sauce thickens, about 5 minutes.
05 - Stir in the Dijon mustard, garlic powder, onion powder, salt, and black pepper until well combined. Remove from heat and set aside.
06 - Spread a thin layer of béchamel sauce across the bottom of the prepared baking dish. Arrange a layer of lasagna noodles over the sauce.
07 - Top the noodles with half of the shredded chicken, half of the sliced ham, and one-third of the Swiss cheese. Spoon additional sauce evenly over the layer.
08 - Add another layer of noodles, followed by the remaining chicken, remaining ham, another third of Swiss cheese, and more sauce.
09 - Finish with a final layer of noodles. Spread the remaining béchamel sauce on top, then sprinkle evenly with the mozzarella and Parmesan cheeses.
10 - Cover the baking dish tightly with aluminum foil and bake for 30 minutes.
11 - Remove the foil and continue baking for an additional 15 to 20 minutes, until the top is golden brown and the sauce is bubbly.
12 - Remove from the oven and let rest for 10 minutes before slicing. Garnish with fresh chopped parsley if desired, then serve.