- Preheat oven to 350°F. Lightly spray a 9x13 baking dish with cooking spray. Set aside. 
- Heat a large skillet over medium heat until hot and then add olive oil. 
- Add chicken to pan and season with salt, pepper, and garlic powder. Cook and brown chicken for 3-4 minutes on each side, or until almost cooked through (chicken will continue to cook in oven). Remove chicken from pan and set aside.  
- While chicken is cooking, prepare pasta according to package directions until al dente. Drain and set aside. 
- To the same skillet, butter and melt over medium heat. Add garlic and saute for 45 seconds. Add flour and continuously whisk for 1 minute. 
- Gradually whisk in heavy cream and milk over medium heat. Once bubbles form on the sides, reduce heat to low, simmer and whisk constantly until slightly thickened, about 2-3 minutes.  
- Add salt, pepper, stir in shredded Parmesan and ½ cup of mozzarella cheeses, and then remove from heat. Continue to stir until melted and smooth. 
- Add cooked pasta and chicken to skillet and stir to combine. Pour into prepared pan and top with remaining ¾ cup mozzarella cheese. Bake for 15-20 minutes, or until mixture starts to bubble around the edges and cheese is melted.