Preparation Steps

• Preheat the oven to 375°F (190°C). Grease a large baking dish or two smaller dishes so one can hold the meatloaf and the other the potato casserole, or arrange them side by side in a single ovenproof pan.
• Place quartered russet potatoes in a large pot and cover with cold water. Add a pinch of salt and bring to a boil, then simmer until potatoes are fork-tender, about 15–20 minutes.
• While potatoes cook, combine ground beef, breadcrumbs, eggs, chopped onion, minced garlic, Worcestershire sauce, salt, and black pepper in a large bowl. Mix gently until just combined — do not overwork the meat.
• Shape the meat mixture into a loaf and place into the prepared baking dish. In a small bowl, stir together ketchup, brown sugar, and mustard; brush half of the glaze over the top of the meatloaf.
• Drain the potatoes and return to the pot. Mash with 2 tablespoons of butter, warmed milk, and sour cream until smooth. Stir in 1.0 cup cheddar cheese and chopped parsley; season with salt and pepper to taste.
• Spoon the mashed potatoes into the second baking dish (or spread around the meatloaf in the same large pan), smoothing the top. Sprinkle the reserved 0.5 cup shredded cheddar over the potatoes and dot with remaining butter.
• Bake in the preheated oven for about 50–60 minutes, or until the meatloaf reaches an internal temperature of 160°F (71°C) and the potato topping is golden and bubbly. If the glaze begins to darken too quickly, tent with foil.
• Remove from oven and let the meatloaf rest 10 minutes before slicing. Serve each portion with a scoop of cheesy mashed potatoes and garnish with additional chopped parsley, if desired.