Preheat your oven to 375F and move the rack to the top third of the oven.
Cut the chicken in half lengthwise to make four thinner cutlets, then season the chicken with salt & pepper.
To a medium bowl, add the ricotta, parmesan, garlic, and Italian seasoning, and mix together.
Pour half of the marinara sauce into a 9x13 casserole dish, and then spread it out evenly.
Arrange the chicken side-by-side in the casserole dish, and spread the ricotta mixture on top of each piece of chicken.
Spoon the rest of the marinara sauce over each piece of chicken.
Tightly cover the casserole dish with foil and bake for 20 minutes.
Take the casserole dish out of the oven, and remove the foil. Sprinkle the mozzarella on top of the chicken, and return it to the oven, uncovered, for 15 minutes or until the chicken is cooked through (165F).
If desired, broil for a couple of minutes to brown the cheese (watch it doesn't burn).
Let the chicken rest for a few minutes prior to serving. Season with extra salt & pepper if needed, and top with fresh basil if using.