1. Heat oven to 375°F. Lightly grease a 9 × 13-inch baking dish.
2. Soak breadcrumbs in ⅓ cup milk for 5 minutes. Stir in eggs, onion, ketchup, Worcestershire, garlic powder, parsley, salt, and pepper. Add beef and mix gently just until combined.
3. Pat into an even layer in the dish. Bake uncovered about 25–35 minutes, or until the center reaches 160°F in several locations. Continue baking as needed to reach temperature.
4. Meanwhile, simmer potatoes in water until fork-tender, about 15–20 minutes after simmering begins. Drain well and let excess moisture evaporate briefly.
5. Mash with butter, sour cream, ¼ cup warm milk, salt, and pepper. Add more milk only as needed for a thick, spreadable mash. Fold in ½ cup cheddar.
6. Carefully spoon or baste pooled fat and liquid from the cooked meat. If using glaze, mix and spread it thinly over the meat.
7. Dollop potatoes over the meat and spread gently. Top with remaining 1½ cups cheddar and half the bacon.
8. Bake another 15–20 minutes, until the cheese melts and the casserole is hot throughout. Rest 10 minutes. Add remaining bacon and green onions before serving.

Make-ahead: Chilled cooked components need a longer covered reheating stage; heat the assembled casserole to 165°F throughout.

Storage: Refrigerate promptly in shallow containers and use within 3–4 days. Reheat leftovers to 165°F. Freeze portions for up to 2 months for best quality.

Estimated nutrition: About 550–680 calories per serving at eight servings, before optional glaze and serving toppings.

Development note: Suggested formula developed from the title; not kitchen-tested. Use temperature and texture cues to adjust timing.