Preheat oven to 375 degrees. In a large skillet, cook the spinach and garlic in oil just until wilted. Drain. Stir in 1 tablespoon Parmesan cheese, salt and pepper.
Pound chicken breasts with a meat mallet to ½-inch thickness. Spread each with 1 tablespoon spinach mixture. Fold the chicken in half, enclosing filling; secure with toothpicks.
Place bread crumbs and egg in separate shallow bowls. Dip chicken in egg, then roll in crumbs to coat. Place seam side down in an 8-inch square baking dish coated with cooking spray. Bake, uncovered, 20 minutes.
Meanwhile, in a large bowl, combine tomato sauce, basil and oregano. Pour over chicken. Sprinkle with mozzarella cheese. Bake, uncovered, 10–15 minutes longer or until a thermometer reads 165 degrees. Discard toothpicks before serving.