Preheat the oven to 200°C (400°F).
Bring a large pot of lightly salted water to a boil. Cook the lasagna noodles in boiling water, stirring occasionally, until cooked through but still firm to the bite, about 8 minutes. Drain.
Melt the butter in a saucepan over medium heat; stir the cream cheese into the hot butter until it begins to melt, about 5 minutes. Season with salt, onion powder, and black pepper. Gradually whisk the hot milk into the cream cheese until smooth; stir in 380 ml of Swiss cheese. Bring the sauce to a simmer, stirring constantly, until the cheese is melted and the sauce has thickened, about 5 to 10 minutes. Remove from the heat.
Spread 190 ml of the cheese sauce in the bottom of a 23 x 23 cm (9 x 9 inch) baking dish. Arrange 1/3 of the lasagna noodles over the sauce and distribute half of the cooked chicken and half of the ham over the noodles. Pour 250 ml of sauce over the chicken and ham.
Repeat the layers, starting with half of the remaining lasagna noodles, the remaining chicken, the remaining ham, and 250 ml of cheese sauce. Finish by layering the remaining lasagna noodles, the remaining sauce, 125 ml of Swiss cheese, and the breadcrumbs; sprinkle with Italian seasoning. Cover the dish with aluminum foil.
Bake in a preheated oven until bubbly, about 25 minutes. Remove the foil and continue baking until the breadcrumbs are golden brown, about 10 minutes more. Let stand for 5 to 10 minutes before serving.
Enjoy!
