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 to remove excess moisture. Generously season both sides with salt and black pepper. Place the seasoned chicken in the prepared baking dish in a single layer.
03 - In a medium bowl, combine Caesar dressing, sour cream (or Greek yogurt), grated Parmesan cheese, minced garlic, Dijon mustard, and lemon juice. Whisk thoroughly until completely smooth and well incorporated.
04 - Spread the creamy sauce mixture evenly over each chicken breast, using a spoon or spatula to ensure the chicken is completely covered on all exposed surfaces.
05 - Sprinkle shredded mozzarella cheese and the additional grated Parmesan cheese evenly over the sauce-coated chicken breasts.
06 - Bake uncovered for 25-30 minutes until chicken is fully cooked through. Internal temperature should reach 165°F when tested with a meat thermometer. The cheese topping should be golden brown and bubbly.
07 - Remove from oven and let the chicken rest for 5 minutes to allow juices to redistribute. Garnish with chopped fresh parsley just before serving.