Preheat your oven to 350°F. While it heats, brown the sausage in a large skillet over medium-high heat, breaking it into small crumbles as it cooks, about 8-10 minutes until no pink remains. Drain excess fat from the cooked sausage and set it aside on a paper towel-lined plate to cool slightly.

In a large bowl, combine the thawed hash browns with salt and black pepper, mixing well to distribute seasonings evenly. Squeeze out any excess moisture from the hash browns if they still feel wet—this prevents a soggy casserole. Stir in the softened cream cheese, breaking it into small pieces as you mix so it distributes throughout the hash browns. The mixture should come together with visible cream cheese throughout.

Spread the hash brown mixture from Step 2 evenly into a 9x13 inch baking dish, pressing gently to create a compact base layer. Scatter the browned sausage from Step 1 over the hash browns, then sprinkle 4 oz of the freshly shredded cheddar cheese over the sausage layer. Reserve the remaining 4 oz of cheddar for topping after the egg custard is added.

Whisk together the flour and milk in a medium bowl until smooth and no lumps remain—the flour acts as a binder to create a silkier custard texture. In a separate large bowl, crack and beat the eggs thoroughly until the yolks and whites are fully combined. Pour the milk mixture into the beaten eggs and whisk until well combined. I like to taste the custard and add a tiny pinch of salt if needed, as it really brings out the savory flavors of the cheese and sausage.

Pour the egg custard from Step 4 evenly over the layered casserole, making sure it seeps into all the nooks and crannies. Sprinkle the remaining 4 oz of cheddar cheese on top as a finishing layer. Place the baking dish in the preheated 350°F oven and bake for 30-40 minutes until the eggs are set in the center (a knife inserted in the middle should come out clean) and the top is golden and slightly puffed. I recommend starting to check at 30 minutes, as oven temperatures vary and you don't want it overcooked and rubbery.

Remove the casserole from the oven and let it rest for 5-10 minutes before cutting and serving. This resting period allows the eggs to finish cooking gently and makes portioning much cleaner. The bake can be served warm or at room temperature and makes great leftovers.