Prepare the Lasagna Noodles:
Cook the lasagna noodles according to package instructions. Drain and set aside. If you’re using no-boil noodles, you can skip this step.
Make the Béchamel Sauce:
In a medium saucepan, melt the butter over medium heat. Add the flour and whisk continuously for 1-2 minutes to make a roux.
Gradually add the milk while whisking to prevent lumps. Continue to cook, whisking constantly, until the sauce thickens (about 5-7 minutes).
Once thickened, stir in garlic powder, onion powder, nutmeg (if using), salt, and pepper. Remove from heat and set aside.
Assemble the Lasagna:
Preheat your oven to 375°F (190°C).
In a greased 9×13-inch baking dish, spread a thin layer of the béchamel sauce on the bottom.
Layer 3 lasagna noodles over the sauce. Top with 1/3 of the shredded chicken, 1/3 of the diced ham, 1/3 of the Swiss cheese, and a drizzle of béchamel sauce.
Repeat the layers two more times, using the remaining noodles, chicken, ham, cheese, and sauce. Finish with a final layer of béchamel sauce, then sprinkle with the grated Parmesan cheese on top.
Bake the Lasagna:
Cover the baking dish with aluminum foil and bake for 25 minutes.
After 25 minutes, remove the foil and bake for an additional 10-15 minutes, or until the cheese is golden and bubbly, and the lasagna is heated through.
Let It Rest:
Once the lasagna is done, let it rest for about 10 minutes before slicing. This helps the layers set and makes it easier to serve.
Serve:
Serve the Chicken Cordon Bleu Lasagna warm, with a side salad or garlic bread for a complete meal.