Wash and peel potatoes, cut into 1-2 inch cubes, and place in a large pot. Fill pot with cold water until it reaches roughly 2 inches above the potatoes. Sprinkle generously with salt, then set over high heat and boil until soft, where a fork can easily poke through.
Meanwhile, heat the oil over medium high heat in a large skillet with sides (or a Dutch oven). When the oil is hot, add in the ground beef. Break into a few large clumps, but avoiding stirring. Sprinkle lightly with salt and pepper. When brown on the bottom, gently flip the beef and break the clumps down a little bit more. Continue until evenly browned and just cooked through.
When the beef is cooked, turn down the burner to medium low. Depending on how much grease is in the bottom of the pan, you may want to drain some off, leaving about 2 tablespoons. Sprinkle flour over the beef and stir until evenly coated, about 1-2 minutes. Slowly pour in 2 cups of water and 1/4 cup milk, stirring constantly until mixed. Cook on low heat until the mixture thickens into gravy. Salt and pepper to taste.
When the potatoes are done, drain off the water and return them to the pot. Mash in butter and remaining 1/2 cup milk. Salt and pepper to taste.
To serve: spoon out a heap of mashed potatoes onto a plate, hollow out a well, and ladle in some beef gravy. Enjoy!
