Preheat the oven to 375°F (190°C).
In a large bowl, combine ground beef, breadcrumbs, eggs, Worcestershire sauce, garlic powder, onion powder, salt, and pepper. Mix until well blended.
Spread the meat mixture evenly in the base of a greased 9x13-inch baking dish.
In a separate pot, bring water to a boil and add the chopped potatoes. Cook until fork-tender, about 15 minutes, then drain.
Mash the potatoes with sour cream, salt, and pepper until smooth and creamy.
Spread the mashed potatoes on top of the meat mixture in the baking dish, smoothing it carefully with a spatula.
Sprinkle shredded cheddar cheese over the mashed potatoes, followed by chopped green onions.
Bake for 30-35 minutes, or until the cheese is melted and bubbly, and the edges are golden brown.
Let the casserole cool for a few minutes before slicing and serving.