Preheat your oven to 375°F (190°C).
In a large skillet, combine the shredded chicken, marinara sauce, garlic powder, Italian seasoning, salt, and black pepper. Heat over medium heat until warmed through, about 5 minutes.
Meanwhile, cook the penne pasta according to package instructions until al dente. Drain and set aside.
In a large mixing bowl, combine the cooked pasta with the chicken and sauce mixture. Stir until the pasta is well-coated.
Transfer half of the chicken and pasta mixture into the greased 9x13-inch baking dish. Sprinkle with half of the mozzarella cheese and half of the grated Parmesan cheese.
Layer the remaining chicken and pasta mixture on top, then add the remaining mozzarella and Parmesan cheese.
Cover the baking dish with aluminum foil and bake in the preheated oven for 30 minutes.
Remove the foil and bake for an additional 10 minutes, or until the cheese is bubbly and golden brown.
Remove from the oven and let it cool for a few minutes before serving. Garnish with chopped fresh basil if desired.