Preheat oven to 350°F and grease a 9x13-inch baking dish.

Bring a large pot of salted water to a boil and cook penne pasta according to package directions. Drain and set aside.

In a medium saucepan over medium heat, melt butter. Whisk in flour and cook for 1-2 minutes until it smells nutty.

Slowly pour in half and half while whisking vigorously. Continue whisking until sauce thickens and starts to bubble.

Reduce heat to low and stir in minced garlic, garlic powder, Italian seasoning, salt, and pepper. Whisk in parmesan until melted. Taste and adjust seasoning.

In a bowl or the pasta pot, combine pasta, cooked chicken, and garlic parmesan sauce. Stir to coat evenly.

Transfer half of the mixture to the prepared baking dish. Top with half of the mozzarella cheese. Repeat with remaining pasta and top with remaining mozzarella.

Bake uncovered for 25-30 minutes until the top is golden and bubbly. Let rest 5-10 minutes before serving. Garnish with parsley if desired.