Prep: Preheat your oven to 375°F (190°C) and lightly grease a 9x13 baking dish.
Season: Rub the chicken breasts with salt, pepper, garlic powder, and paprika on both sides. Arrange them in a single layer in the baking dish.
Mix: In a medium bowl, beat together the softened cream cheese, sour cream, mayonnaise, cheddar, Parmesan, garlic, and onion powder until the mixture is uniform and smooth.
Layer: Spread the creamy mixture thick and even over each piece of chicken, making sure to seal the edges to trap the moisture.
Top: Sprinkle the mozzarella cheese over the top if you're looking for that extra "cheese pull" finish.
Bake: Bake uncovered for 35–45 minutes. The chicken is done when it reaches an internal temperature of 165°F (74°C) and the cheese topping is golden and bubbling.
Rest: Let the dish rest for 5–10 minutes before serving. This is a critical step to allow the creamy sauce to thicken slightly.
Serve: Garnish with fresh parsley and serve warm.