Note: The following recipe is for the homemade version making your own white sauce. If you want the recipe using a can of cream of chicken soup, see notes below!
If you have time, open your package of frozen hash browns and put it in a colander over the sink. Let the potatoes thaw for 2-4 hours. If you let them thaw, the potatoes will turn out slightly softer. If you are in a hurry, you can add the potatoes to this dish completely frozen (I tried it both ways). The potatoes will be slightly more firm but they still taste great. I do recommend thawing if you have time.
Preheat your oven to 350 degrees F. Spray a 9x13 inch pan
with nonstick spray, or rub with butter.
In a large bowl, melt 1/4 cup butter. Add the potatoes (thawed or frozen) and stir together to coat with butter.
Add 2 cups of cheddar cheese (pack it well) and 1 and 1/2 cups sour cream.
Make the white sauce: In a medium skillet, melt 1/4 cup butter over medium heat. Add 1/2 an onion, chopped. Let the onion saute in the butter for about 3-5 minutes, until they are starting to look translucent.
Add 2 teaspoons garlic and saute for 1 more minute, until fragrant.
Add 1/4 cup flour a little bit at a time, stirring constantly. (Incorporate the flour into the butter by stirring, then add a bit more, etc.) Once all the flour is added, continue to cook over medium heat for about 1 minute to cook out the "raw" flour taste.
Slowly add 1/2 cup chicken broth, using the same method as before. Add a little bit while stirring constantly, and once it is incorporated, at more. Do the same thing with 1/2 cup milk.
Stir the mixture until all the liquid has been absorbed. You should have a thick white sauce.
Season with 1 teaspoon salt and 1/2 teaspoon pepper.
Add the white sauce to the potato mixture. Stir it all together.
Add the potatoes to the prepared 9x13 inch pan. Spread evenly.
In a medium bowl, melt 1/4 cup butter.
In a small bowl, add 3 cups corn flakes. Use your hands to crush them a little bit. It doesn't have to be perfect, some larger flakes is okay. Dump the corn flakes into the bowl with the melted butter (and wipe out the small bowl and put it back in the cupboard.) You could also crush the corn flakes in a ziplock bag if you prefer.
Coat the corn flakes with butter and spread evenly on top of the potatoes
Bake (do not cover) at 350 for about 40-50 minutes, until some of the corn flakes are starting to brown and it looks bubbly around the edges.
Let sit for a few minutes to settle and then dig in! This goes really well with ham