Start by preheating your oven to 400°F (204°C). Lightly grease a 9x13-inch baking dish to prevent sticking. Take your chicken breasts and butterfly them lengthwise. Be careful not to cut all the way through—just open them like a book. Lay them flat in the prepared dish. This cut gives you a perfect pocket for stuffing.
In a small mixing bowl, combine the ricotta cheese, one egg, two teaspoons of Italian seasoning, the crushed garlic, ½ teaspoon salt, and 1 cup of shredded mozzarella. Stir until smooth. This creamy mixture will mimic the filling of classic lasagna and become the flavorful core of each chicken breast.
Spoon about ½ cup of marinara sauce onto one side of each butterflied chicken breast. Then, layer the ricotta mixture on top of the sauce. Fold the chicken over to close it, creating a stuffed pocket. You may need to gently press the edges together to keep the filling in place.
Drizzle the remaining ½ cup of marinara sauce over the top of the folded chicken breasts. Sprinkle the remaining 1 cup of shredded mozzarella evenly over everything. Finish by dusting the tops with the last teaspoon of Italian seasoning, remaining ½ teaspoon salt, and black pepper for extra flavor.
Place the baking dish in the oven and bake for 25 to 30 minutes. The cheese should be melted and bubbling, and the chicken should reach an internal temperature of 165°F (74°C). Let it rest for a few minutes before serving to lock in the juices and let everything settle.