Preheat your oven to 350°F and grease a 9x13-inch baking dish with 2 tablespoons of butter. Spread the 2 lbs of frozen shredded hashbrowns evenly across the bottom, creating an even layer that will cook uniformly throughout the casserole.

In a large bowl, whisk together the 8 eggs, 1 cup heavy cream, 1 cup whole milk, garlic powder, black pepper, and salt until completely combined. This egg mixture is your binding agent that transforms the hashbrowns into a cohesive, creamy casserole as it bakes.

Sauté the diced bell peppers and onions in 2 tablespoons of butter over medium heat for 5-7 minutes until softened and fragrant. Transfer the softened vegetables to the egg mixture, then fold in the diced smoked turkey and 1/2 cup sour cream until fully incorporated.

Sprinkle 1 cup sharp cheddar cheese and 1 cup mozzarella cheese over the hashbrown layer, then pour the creamy egg and vegetable mixture evenly across the top. Stir gently to distribute the loaded hashbrown filling without breaking apart the potato pieces too much.

In a small bowl, combine the 1/2 cup panko breadcrumbs with 2 tbsp fresh chives and remaining seasonings, then sprinkle this topping across the casserole surface. Bake for 40 minutes until the top turns golden brown and a knife inserted in the center comes out clean.

Remove from the oven and let the golden loaded hashbrown casserole rest for 5 minutes before serving, allowing the custard to set fully and making portioning much cleaner and easier.