Prepare the potatoes: Peel and chop the potatoes into medium-sized cubes. Add the potatoes to a pot and cover with 800 ml of water. Bring to a boil and cook for about 10-12 minutes or until the potatoes are tender when pierced with a fork.
Cook the ground beef: While the potatoes are boiling, heat a pan over medium heat. Add the ground beef and cook until browned, breaking it up as it cooks. Season with salt and pepper to taste. Add the finely chopped onion to the beef and sauté until softened, about 5 minutes. Stir occasionally to avoid burning the meat.
Combine: Once the potatoes are cooked, drain them and return them to the pot. Mash the potatoes until smooth. Stir in the cooked ground beef and onion mixture until everything is well combined.
Serve: Transfer the mashed potato and beef mixture to serving plates. Top with a generous spoonful of mayonnaise for added creaminess and flavor.
Enjoy: Serve warm and enjoy the comforting, savory goodness of this simple yet satisfying dish!