Loaded Hamburger Steak Casserole

0 Bring a pot of water to boil and boil the diced potatoes until fork tender.  While the potatoes are boiling, add the olive oil, onions and mushrooms to a large skillet over medium-high heat. Allow them to cook for 2-3 minutes then add in the ground beef. Cook until you don't see any pink then season with seasoned salt and drain off the excess grease. Set aside for now.
1 In the same skillet on low heat add in 6 tablespoons of butter.  Once its melted sprinkle in the flour. Mix the two together, stirring constantly, allow it to cook for 2-3 minutes. Pour in the beef broth and packet of Lipton Beefy Onion Soup Mix and whisk together. Bring to a simmer while stirring occasionally. Once it reaches a thicker consistency, set some gravy aside for topping the casserole with and then add in the ground beef. Stir everything together and transfer to a 9x13 casserole dish.
2 Once the potatoes are fork tender, drain the excess water and pour them into a mixing bowl. Add in the butter and allow it to melt. Once melted, add in the milk, season with salt & black pepper to taste and mash together with a potato masher or an electric hand mixer. Once they have a whipped smooth consistency, pour them on top of the meat mixture and smooth off the top.
3 Top the casserole with the gravy you set to the side, serve & enjoy!