Cook the pasta: Boil the pasta in salted water until just al dente, then drain well and set it aside.
Prepare the chicken: Cut the chicken into even bite-sized pieces and season with Italian seasoning, salt, and black pepper.
Brown the chicken: Heat olive oil in an oven-safe skillet and cook the chicken for 5 to 6 minutes until golden and cooked through, then transfer it to a plate.
Cook the garlic and tomatoes: Lower the heat, cook the minced garlic briefly, then stir in the chopped sun-dried tomatoes and warm them through.
Make the sauce: Add chicken broth and heavy cream, scrape up the browned bits, and simmer gently for 2 to 3 minutes.
Add Parmesan: Stir in Parmesan until melted and smooth, adding red pepper flakes if desired.
Combine: Return the chicken and pasta to the skillet and stir until everything is evenly coated in sauce.
Top and bake: Cover the pasta with shredded mozzarella and bake at 400°F for 10 to 15 minutes until bubbling and melted.
Brown and rest: Broil for 1 to 2 minutes if desired, then let the bake rest for 5 minutes before serving.