Prep the oven and pan: Preheat the oven to 400°F (200°C).
Lightly grease a 9x13-inch baking dish with cooking spray or a thin coat of olive oil.
Butterfly or pound the chicken: For even cooking, pound the chicken breasts to about 3/4-inch thickness or slice them in half horizontally if they’re very thick. Pat dry with paper towels.
Season the chicken: Drizzle breasts with 1 tablespoon olive oil. Sprinkle 1 tablespoon ranch seasoning, salt, pepper, and paprika over both sides.
Lay them in the baking dish in a single layer. If using veggies, tuck them around the chicken.
Make the ranch topping: In a bowl, mix Greek yogurt, cream cheese, Parmesan, remaining 1 tablespoon ranch seasoning, and garlic until smooth. Taste and adjust salt if needed.
Spread and top: Spoon the ranch mixture evenly over the chicken.
Sprinkle shredded mozzarella over the top.
Bake: Place the dish on the middle rack and bake for 20–25 minutes, or until the chicken reaches an internal temperature of 165°F (74°C). If you want extra browning, broil for 1–2 minutes at the end, watching closely.
Rest and garnish: Let the chicken rest for 5 minutes. Sprinkle with sliced chives or green onions before serving.
Serve: Pair with a simple side like roasted green beans, a mixed salad, or quinoa for a complete high-protein plate.