Preheat oven to 350°F (175°C). Lightly grease a 9x13 inch baking dish.

Place cubed potatoes in a large pot of salted water. Bring to a boil and cook for 10-12 minutes until fork-tender. Drain well and set aside in a large mixing bowl.

Heat a skillet over medium-high heat. Add the ground beef and cook, breaking it into very small crumbles, until browned and crispy. Drain excess fat.

To the warm potatoes, add the sour cream, melted butter, milk, salt, pepper, and garlic powder. Mix gently so the potatoes remain mostly intact.

Fold in 1.5 cups of the shredded cheddar cheese, half of the crispy beef crumbles, and half of the sliced green onions.

Spread the potato mixture evenly into the prepared baking dish. Top with the remaining 0.5 cup of cheddar cheese and the remaining crispy beef.

Bake uncovered for 20-25 minutes, or until the cheese is melted and bubbly around the edges.

Remove from the oven and garnish with the remaining green onions. Serve warm.