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1
Preheat oven to 400 degrees F (200 degrees C).
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2
Bring a large pot of lightly salted water to a boil. Cook lasagna in the boiling water, stirring occasionally until cooked through but firm to the bite, about 8 minutes. Drain.
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3
Melt butter in a saucepan over medium heat; stir cream cheese into hot butter until it begins to melt, about 5 minutes. Season with salt, onion powder, and black pepper. Whisk warm milk gradually into cream cheese until smooth; stir in 1 1/2 cup Swiss cheese. Bring sauce to a simmer, stirring constantly, until cheese has melted and sauce has thickened, 5 to 10 minutes. Remove from heat.
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4
Spread 3/4 cup of cheese sauce into bottom of a 9x9-inch baking dish. Arrange 1/3 of the lasagna noodles over the sauce and spread half the cooked chicken and half the ham over the noodles. Pour 1 cup sauce over chicken and ham. Repeat layers starting with half the remaining lasagna noodles, remaining chicken, remaining ham, and 1 more cup of cheese sauce. Finish by layering remaining lasagna noodles, remaining sauce, 1/2 cup Swiss cheese, and bread crumbs; sprinkle top with Italian seasoning. Cover dish with aluminum foil.
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5
Bake in the preheated oven until casserole is bubbling, about 25 minutes. Remove foil and continue to bake until crumbs are browned, about 10 more minutes. Let casserole stand 5 to 10 minutes before serving.
