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.