In a large pot or skillet, heat a drizzle of olive oil over medium-high heat. Season the boneless skinless chicken breasts with salt and pepper, then add them to the hot pan. Sear for about 5 minutes until golden brown, then flip and cook for an additional 3-4 minutes. The chicken should not be fully cooked; remove it from the pot and set it aside on a plate.

Using the same pot, add the diced onion and minced garlic. Sauté over medium heat for 2-3 minutes, stirring frequently until the onion is translucent and the garlic is fragrant.

Pour in the marinara sauce and one cup of water, scraping the bottom of the pot to release any browned bits. Stir well and bring the mixture to a gentle boil.

Return the seared chicken to the pot along with the dried pasta. Stir everything together to ensure the pasta is well-coated in sauce. Cover the pot and reduce the heat to low, allowing it to simmer for 10-15 minutes.

Once the pasta is cooked, stir in the freshly grated Parmesan cheese and 1/4 cup of shredded mozzarella. Mix until the cheeses are melted.

Transfer the pasta mixture into a baking dish, spreading it evenly. Sprinkle the remaining mozzarella cheese generously on top. Place the dish under the broiler for 2-3 minutes, or until the cheese is bubbly and golden brown.

Remove the baking dish from the oven and let it rest for a few minutes. Top with torn basil leaves and chopped parsley before serving.