Preheat your oven to 400°F (200°C). Slice the top off the head of garlic to expose the cloves, drizzle with a little olive oil, wrap it tightly in foil, and roast for about 30-40 minutes until soft and golden. Once cooled, squeeze out the roasted garlic cloves and mash into a smooth paste.
While the garlic roasts, bring a large pot of salted water to a boil. Add the penne pasta and cook according to package instructions until al dente (usually around 10-12 minutes). Drain and set aside.
In a large skillet, heat the olive oil over medium-high heat. Season the diced chicken breast with salt, pepper, and Italian seasoning. Add the chicken pieces to the skillet and cook, stirring occasionally, until browned on all sides and cooked through, about 6-8 minutes. Remove from heat.
In the same skillet, reduce heat to medium. Stir in the mashed roasted garlic and heavy cream, mixing until well combined. Bring to a gentle simmer and then add the grated Parmesan cheese, stirring until the cheese melts and the sauce thickens slightly. Taste and adjust seasoning with salt, pepper, and a pinch more Italian seasoning if desired.
Add the cooked penne pasta and sautéed chicken into the skillet with the Alfredo sauce. Toss gently to coat everything evenly in the creamy sauce.
Transfer the pasta mixture into your prepared baking dish. Sprinkle the shredded mozzarella evenly over the top.
Bake uncovered at 375°F (190°C) for 20-25 minutes or until the cheese is bubbly and lightly browned. Optionally, broil for an additional 2-3 minutes for extra golden crispiness, watching closely to prevent burning.
Once baked, remove from the oven and let it rest for 5 minutes. Sprinkle with freshly chopped parsley for a pop of color and freshness. Serve hot with a side salad or steamed vegetables.