Preheat oven to 375 degrees.
Cook pasta according to package directions. Drain and return pasta back into the large pot.
While the pasta is cooking, start making the alfredo sauce. Over medium heat, add the butter and garlic to a large pot. Sauté for 1-2 minutes, stirring constantly. Stir in the flour and sauté for an additional 1 minute.
Slowly add the chicken broth and whisk to combine. Make sure to continue to whisk until it’s smooth, about 2 minutes. Whisk in milk and bring mixture to a low simmer, let cook until thickened. Make sure to stir occasionally.
Once thickened, add the grated parmesan cheese, Italian seasoning, and salt & pepper. Mix well until all the cheese is melted and incorporated.
In the pot with the drained pasta, add the alfredo sauce and chicken. Mix well.
Spray a 9x13 pan with cooking oil spray and pour in half the pasta. Sprinkle with 1 cup of mozzarella cheese then add the other half of the pasta mixture. Top with the remaining mozzarella cheese.
Bake for 20-25 minutes. Remove from oven and serve immediately. Sprinkle with additional grated parmesan cheese and Italian seasoning if desired.