Au Gratin Hash Brown Casserole

Au Gratin Hash Brown Casserole
These Au Gratin Hash Brown Potatoes are the definition of comfort food! Like a loaded baked potato in casserole form! Perfect for parties and holidays.
Course: Side Dish
Cuisine: American
Keyword: Hash Brown Casserole
Prep Time: 15 minutes
Cook Time: 1 hour
Total Time: 1 hour 15 minutes
Servings: 12
Calories: 300 kcal
Author: Jaclyn


  • 1 (30 oz) package frozen shredded hash brown potatoes, thawed
  • 4 Tbsp butter, diced into 1 Tbsp pieces
  • 1/2 cup finely chopped yellow onion
  • 1/4 cup all-purpose flour
  • 2 3/4 cups milk (whole or 2%)
  • 1 1/2 cups shredded sharp cheddar cheese
  • 1/2 cup finely shredded parmesan cheese
  • 1 cup sour cream
  • Salt and freshly ground pepper
  • 4 cups cornflakes, crushed (nearly 2 cups once crushed)
  • 3 Tbsp butter, melted
  • 1 1/2 Tbsp chopped fresh parsley


  1. Preheat oven to 350 degrees.

  2. Melt 4 Tbsp butter in a large saucepan over medium heat. Add onion and saute until softened, about 5 - 6 minutes. 

  3. Add in flour and cook stirring constantly, 1 minute. While whisking pour in milk then cook stirring constantly until mixture comes to a boil.

  4. Remove from heat, add in cheddar cheese and parmesan cheese and stir until melted. 

  5. Stir in sour cream. Season mixture with salt and pepper to taste (you want it on the salty side as it will be seasoning the potatoes).

  6. Place hash browns in a large mixing bowl then pour in milk mixture and toss to evenly coat. Transfer to a 13 by 9-inch baking dish (no need to grease dish) and spread into and even layer.

  7. Place cornflakes in a gallon size resealable bag, seal bag and crush with a rolling pin to roughly pebble size bits. 

  8. Add 3 Tbsp melted butter to cornflake mixture then seal bag and toss to evenly coat with butter. Sprinkle cornflake mixture evenly over casserole.

  9. Bake in preheated oven until hot throughout, about 40 - 50 minutes. Garnish with parsley and serve warm.

  10. Recipe source: Cooking Classy