Rinse 2 large russet potatoes under running water, scrubbing off as much surface dirt as possible. After rinsing potatoes, peel potatoes completely and place on cutting board.
Carefully slice potatoes into ¼-inch-thick coins using sharp knife or mandoline slicer. Exact number of potato coins will depend on size of potatoes.
Once both potatoes have been sliced into coins, place potatoes in large pot and fill pot with enough water that waterline sits approximately 2 inches above top layer of potatoes.
Sprinkle 1 tablespoon salt into water and place pot on stovetop over high heat. Bring water to rolling boil and boil potatoes 6 to 7 minutes or until potatoes can be easily pierced with fork. Be careful not to overcook potatoes.
Once potatoes are fork-tender, pour water and potatoes into colander. Drain potatoes well and set aside.
While potatoes boil, place large skillet on stovetop over medium heat. Add 1 pound ground beef to skillet and cook, breaking up ground beef with wooden spoon or spatula, until meat is browned and crumbled, approximately 7 to 10 minutes.
When ground beef is browned, add 1 cup diced onion and stir to incorporate. Sauté onions with ground beef 2 to 3 minutes or until onions are softened.
Add 2 cloves garlic and stir to incorporate. Sauté mixture 30 to 60 seconds or until garlic is just fragrant. Once garlic is fragrant, carefully drain any fat from skillet, then return skillet to heat.
Add 2 teaspoons white wine vinegar to skillet and stir to incorporate, making sure to scrape up any browned bits of food that may have stuck to bottom of skillet.
Add 1 10.5-ounce can condensed cream of mushroom soup, 1 cup water, and 1 tablespoon dijon mustard to skillet. Stir until ingredients are fully combined and well incorporated.
Increase heat under skillet to medium-high. Once sauce begins to bubble, reduce heat to medium low and simmer sauce 5 to 6 minutes or until thickened.
Add boiled potatoes to skillet and gently stir to incorporate. Taste sauce and stir in salt and freshly ground black pepper as desired.
Simmer mixture until potatoes are warmed through. Divide mixture into preferred portion sizes and transfer to serving plates or bowls. Serve warm.