For the Mashed Potatoes:
Boil the potatoes: Place the peeled and cut potatoes in a large pot. Cover with cold water and add a pinch of salt. Bring to a boil over medium-high heat, then reduce to a simmer. Cook for about 15-20 minutes, or until the potatoes are tender when pierced with a fork.
Mash the potatoes: Drain the potatoes and return them to the pot. Add the butter, milk, and sour cream (if using). Mash until smooth and creamy. Season with salt and pepper to taste. Cover and keep warm.
For the Ground Beef and Gravy:
Cook the ground beef: In a large skillet, heat the olive oil over medium heat. Add the chopped onion and cook until softened, about 3-4 minutes. Add the garlic and cook for an additional minute.
Brown the beef: Add the ground beef to the skillet. Cook, breaking it up with a spoon, until browned and cooked through, about 6-8 minutes. Season with salt and pepper.
Make the gravy: Sprinkle the flour over the beef mixture and stir well, cooking for about 1-2 minutes to get rid of the raw flour taste. Slowly pour in the beef broth while continuously stirring to prevent lumps. Add the Worcestershire sauce and soy sauce (if using). Simmer the gravy for 5-7 minutes, or until it thickens to your desired consistency. Adjust seasoning as needed.
Serve: Spoon the mashed potatoes onto plates, and top with the ground beef and gravy mixture. Garnish with freshly chopped parsley if desired.
