Cook the Pasta: Bring a large pot of salted water to a boil. Cook pasta until al dente. Drain and set aside.
Prepare the Chicken: Heat olive oil in a skillet over medium heat. Season chicken with salt and pepper. Cook for 6-8 minutes (for breasts) or 15-18 minutes (for thighs) until fully cooked. Set aside.
Make the Cheese Sauce: In a saucepan, melt butter over medium heat. Whisk in flour and cook for 1 minute. Slowly add half and half and heavy cream, whisking constantly. Add cheddar, Parmesan, garlic powder, and paprika. Stir until smooth.
Assemble the Casserole: Preheat oven to 400°F (200°C). In a mixing bowl, combine cooked pasta, chicken, and cheese sauce. Pour into a greased 9x13 inch baking dish. Top with mozzarella cheese.
Bake: Place in oven and bake for 20-30 minutes until cheese is melted and golden brown.
Serve: Garnish with fresh parsley and serve warm.