Preheat oven to 190°C (375°F). Lightly grease a 20x20cm (8x8 inch) baking dish.
In a large bowl, mix softened cream cheese, hot sauce, and ranch dressing until completely smooth with no lumps — about 1 minute with a hand mixer or 2 minutes by hand.
Fold in shredded chicken, 1/2 cup cheddar, all the mozzarella, and garlic powder until evenly combined.
Spread mixture into the prepared dish. Scatter the remaining 1/4 cup cheddar evenly across the top.
Bake uncovered for 20–22 minutes until edges bubble actively and top cheese is golden in spots.
Rest 3 minutes. Garnish with green onions and serve warm directly from the dish.