01 -  Combine ground beef, breadcrumbs, egg, ketchup, salt, and black pepper in a large mixing bowl. Mix until well incorporated. 
 02 -  Form the mixture into a loaf shape and place it in a baking dish. Bake at 350°F (177°C) for 1 hour, or until internal temperature reaches 160°F (71°C). 
 03 -  Place the peeled and quartered potatoes in a large pot and cover with cold water. Add a pinch of salt and bring to a boil. Cook until the potatoes are fork-tender, about 20 minutes. 
 04 -  Drain the cooked potatoes and return them to the pot. Add butter and warmed milk. Mash until smooth and creamy, seasoning with salt and pepper to taste. 
 05 -  Slice the meatloaf and serve alongside generous portions of mashed potatoes.