Preheat your oven to 375°F (190°C). Cook the penne pasta according to package directions until al dente, then drain and set aside. While the pasta cooks, heat olive oil in a large oven-safe skillet over medium heat. Add the cubed chicken and cook until golden brown and cooked through, about 6-8 minutes. Remove chicken and set aside.

In the same skillet, add the diced onion and cook until softened, about 3-4 minutes. Add the minced garlic and cook for another minute until fragrant. Pour in the chicken broth to deglaze the pan, scraping up any browned bits. Stir in the heavy cream and pesto until well combined.

Return the cooked chicken to the skillet along with the drained pasta. Stir everything together until the pasta and chicken are evenly coated with the sauce. Sprinkle with Italian seasoning, salt, and pepper to taste.

Top the pasta mixture with shredded mozzarella and grated Parmesan cheese. Transfer the skillet to the preheated oven and bake for 15-20 minutes, or until the cheese is melted and bubbly with golden spots.

Remove from oven and let it rest for 5 minutes before serving. Garnish with fresh basil leaves if desired.