Hashbrown Casserole Recipe

Prepare oven and dish

Preheat the oven to 350°F (175°C). Lightly grease a 9x13-inch (23x33 cm) baking dish with butter or nonstick spray.

Thaw and drain hashbrowns

If using frozen shredded hashbrowns, ensure they are fully thawed. Place the thawed hashbrowns in a colander and press gently or wrap in a clean kitchen towel to remove excess moisture. Excess water will make the casserole watery.

Sauté onion (optional)

In a small skillet over medium heat, melt 1 tablespoon of the melted butter and sauté the finely diced onion for 3–4 minutes until softened and translucent. This mellows the onion flavor; you can skip this step and use raw diced onion if preferred.

Mix wet ingredients

In a large mixing bowl, combine the sour cream, cream of chicken soup, remaining melted butter (reserve 1 tablespoon for topping if desired), and the egg. Whisk until smooth and fully combined.

Add seasonings and cheeses

Stir in the garlic powder, onion powder, kosher salt, and black pepper until evenly distributed. Fold in 1 3/4 cups of the grated cheddar and all of the mozzarella; reserve 1/2 cup cheddar for topping. Add the sautéed (or raw) onion.

Combine with hashbrowns

Add the drained hashbrowns to the mixing bowl. Using a spatula, fold everything together until the potatoes are evenly coated with the creamy mixture and cheese is well distributed.

Transfer to baking dish

Scrape the hashbrown mixture into the prepared 9x13-inch baking dish and spread it into an even layer, pressing gently to compact slightly so the casserole holds together when sliced.

Prepare topping

In a small bowl, combine the breadcrumbs (or crushed cornflakes) with the 2 tablespoons melted butter and mix until evenly moistened. Stir in the reserved 1/2 cup grated cheddar.

Top casserole

Evenly sprinkle the breadcrumb-cheddar mixture over the top of the casserole. If you reserved one tablespoon of melted butter earlier, drizzle it over the topping for extra browning.

Bake

Place the casserole in the preheated oven and bake uncovered for 30–40 minutes, until the top is golden brown and the edges are bubbling. If you prefer a deeper brown top, you can broil on high for 1–2 minutes at the end — watch closely to avoid burning.

Rest and garnish

Remove from the oven and let the casserole rest for 10 minutes to set. Sprinkle chopped fresh chives over the top before serving, if using. Slice into squares and serve warm.