Peel the potatoes and grate them. Add them to a sieve and rinse them with cold water, removing the starching outer later. Drain the grated potatoes through a clean kitchen towel and add the salt. Mix to combine and set aside for more moisture to be released.
2 lb potatoes, 1 tsp salt
Meanwhile, in a medium-sized pan over medium-high heat and add the olive oil followed by the diced onion and ground beef. Cook briefly for 2-3 minutes, breaking up the ground beef into small chunks. The beef and onion don't have to be fully cooked at this stage.
Add the minced garlic, salt, pepper, and Italian seasoning. Cook for 1-2 minutes until softened and fragrant while stirring.
2 garlic cloves, 1 tsp Italian herbs, 1/2 tsp salt, 1/2 tsp ground black pepper
Reduce the heat to medium-low and sprinkle the flour over the beef mixture. Stir to combine as the mixture will thicken. Slowly pour in the milk while stirring. Add the mozzarella cheese and mix to combine. Transfer the creamy beef mixture to a 9 x 13 inch baking dish.
1 cup milk, 1/2 cup mozzarella cheese, 2 tbsp all-purpose flour
Again, drain any liquid out off the grated potatoes through the kitchen towel. Add the olive oil, pepper, garlic powder, and grated parmesan cheese. Mix to combine.
1/2 tsp ground black pepper, 1 tbsp olive oil, 1/2 cup parmesan cheese, 1/2 tsp garlic powder
Add the shredded hash brown mix evenly on top of the creamy beef. Make sure not to flatten it too much. You want the hash brown layer to have crispy peaks. Bake for 35 minutes and switch on the grill or broiler for the last 5 minutes for the hash brown layer to be crispy and golden brown.
Remove the beef and hash brown casserole from the oven and let it set for 10 minutes before serving. Enjoy!
Notes
Beef: Undercook the ground beef initially so it doesn't become dry and rubbery during the oven baking.Cover: If the casserole is getting too dark during baking, cover it with foil.Storage: Leftovers can be stored in an airtight container in the refrigerator for up to 3 days. For longer storage, you can store it in the freezer for up to 3 months. Simply thaw it at room temperature and reheat it in the oven or microwave.