Heat the oven to 375 degrees and line a baking sheet with parchment paper.
In a large bowl, combine the ground beef, breadcrumbs, milk, onion, egg, allspice, salt, and black pepper. Mix until the ingredients are evenly distributed.
Divide the mixture into four equal portions and shape each into a small loaf. Place the loaves on the prepared baking sheet.
Bake the meatloaves for 25 minutes.
While the meatloaves bake, place the potato chunks in a saucepan and cover with water. Bring to a boil and cook until the potatoes are soft, about 15 minutes.
Drain the potatoes, then return them to the pan. Add the butter, heavy cream, and nutmeg. Mash until smooth.
Remove the meatloaves from the oven. Spoon the mashed potatoes evenly over each loaf.
Return the topped meatloaves to the oven and bake for 10 more minutes until the potato topping starts to brown at the edges.