Step 1: Preheat the Oven
Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch casserole dish.
Step 2: Prepare the Mixture
In a large mixing bowl, combine the cream of chicken soup, cream of mushroom soup, sour cream, milk, garlic powder, onion powder, and paprika. Mix until smooth.
Stir in the thawed hashbrowns, shredded chicken, diced onion, bell pepper (if using), and 1 1/2 cups of shredded cheddar cheese. Mix until evenly combined.
Step 3: Assemble the Casserole
Spread the mixture evenly into the prepared casserole dish.
Sprinkle the remaining 1/2 cup of cheddar cheese over the top.
If using the topping, mix the crushed cornflakes or breadcrumbs with melted butter and sprinkle over the cheese layer.
Step 4: Bake
Cover the dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 20-25 minutes, or until the casserole is bubbling and the top is golden brown.
Step 5: Serve
Let the casserole rest for 5 minutes before serving. Garnish with fresh parsley if desired and pair with a crisp green salad or roasted vegetables for a complete meal.