Preheat your oven to 350°F and butter a 9x13-inch baking dish generously. Place your frozen hashbrowns on a clean kitchen towel and squeeze out as much moisture as possible—this prevents a watery casserole. Spread the dried hashbrowns evenly across the bottom of the prepared dish.

Heat 1 tbsp butter in a large skillet over medium heat, then sauté the diced onion and red bell pepper for 4-5 minutes until softened. Add the chopped smoked turkey and cook for 2 more minutes until warmed through. Distribute this mixture evenly over the hashbrowns in your baking dish.

In a large mixing bowl, whisk together 8 eggs, heavy cream, whole milk, garlic powder, salt, black pepper, and paprika until completely combined. Pour this custard mixture slowly over the hashbrowns and turkey layer, tilting the dish gently to distribute it evenly.

Sprinkle the shredded sharp cheddar and mozzarella cheeses evenly across the top of the golden hashbrown casserole crowd, then scatter the fresh chives over the cheese. Combine panko breadcrumbs with a pinch of paprika and distribute over the top for a golden crust.

Bake uncovered for 35 minutes until the eggs are set but the center still jigles slightly when you gently shake the dish. The top should be golden brown and the edges bubbling. Let the casserole rest for 5 minutes before cutting and serving.