Preheat the oven: Begin by preheating your oven to 375°F (190°C). Grease a 9x13 casserole dish with a little butter or cooking spray.
Cook the pasta: In a large pot of salted boiling water, cook 1 lb of cavatappi pasta until al dente, about 7-8 minutes. Drain and set aside.
Prepare the sauce: In a mixing bowl, combine 2 cans of cream of chicken soup, 2 cups of half & half, 3 tbsp of Dijon mustard, 1 tbsp of fresh parsley, 1 tsp of seasoned salt, and ½ tsp of black pepper. Mix well.
Add cheese and chicken: Stir in 3 cups of shredded Swiss cheese, 2 cups of diced rotisserie chicken, and the cooked pasta into the sauce until evenly coated.
Assemble the casserole: Pour the pasta mixture into the prepared casserole dish, spreading it evenly.
Prepare the topping: In a small bowl, combine 1 tbsp of melted butter, ½ cup of panko breadcrumbs, and ¼ cup of grated Parmesan cheese. Stir until combined, then sprinkle evenly over the chicken mixture.
Bake: Place the casserole in the preheated oven and bake for 25-30 minutes or until the top is golden brown and the casserole is bubbling.