01 - Preheat oven to 400°F. Lightly grease a 9x13-inch baking dish with cooking spray or a small amount of oil.
02 - Pat chicken breasts dry with paper towels. Season both sides generously with salt and black pepper. Arrange in the prepared baking dish in a single layer.
03 - In a medium bowl, combine Caesar dressing, sour cream (or Greek yogurt), grated Parmesan, minced garlic, Dijon mustard, and lemon juice. Whisk until completely smooth and well combined.
04 - Spread the sauce evenly over the chicken breasts, using a spatula or spoon to ensure each piece is fully coated.
05 - Sprinkle shredded mozzarella and additional grated Parmesan cheese evenly over the sauced chicken.
06 - Bake uncovered for 25-30 minutes, or until chicken is cooked through (internal temperature reaches 165°F) and the cheese topping is golden brown and bubbling.
07 - Remove from oven and let chicken rest for 5 minutes before serving. Garnish with chopped fresh parsley if desired.