1 (8 ounce) package lasagna noodles (about 9 noodles)
1/2 cup butter (1 stick)
1 (8 ounce) package cream cheese, softened
1/2 teaspoon salt
1/2 teaspoon onion powder
1/4 teaspoon ground black pepper
2 cups shredded Swiss cheese , divided
1 3/4 cups warm milk
2 1/2 cups rotisserie chicken , diced
8 ounces deli ham , chopped
1/2 cup bread crumbs
1 pinch Italian seasoning , or to taste
Preheat oven to 400 degrees F
Bring a large pot of salted water to a boil. Cook lasagna noodles in the boiling water until cooked through but firm to the bite, about 8 minutes. Drain.
Melt the butter in a saucepan over medium heat and stir in cream cheese into hot butter until it begins to melt, about 5 minutes. It might look strange here! Don't worry. This is normal. Season with salt, onion powder, and black pepper. Whisk warm milk gradually into cream cheese until smooth; make sure to do it slowly. Stir in 1 1/2 cups of Swiss cheese.
Bring the sauce to a simmer, whisking continually until cheese has melted and sauce has thickened, about 5 to 10 minutes. Remove mixture from heat.
Spread a thin layer of cheese sauce onto the bottom of a 9x9-inch baking dish.
Arrange 1/3 of the lasagna noodles over the sauce (3 noodles for me). You can tear them to fit as needed. 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, remaining 1/2 cup Swiss cheese, and bread crumbs; sprinkle top with Italian seasoning. Cover dish tightly with aluminum foil.
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 10 minutes before serving.