How to Make It
Preheat the oven to 400°. In a large saucepan, cover the potatoes with water and bring to a boil. Add a generous pinch of salt and simmer over medium heat until tender, about 25 minutes.
Meanwhile, in a spice grinder, combine the allspice berries, fennel seeds, and black peppercorns; grind into a fine powder. In a large skillet, heat the olive oil until shimmering. Add the ground beef, ground spices, and a generous pinch of salt. Cook over medium-high, breaking up the meat with a wooden spoon, until just starting to brown, about 6 minutes.
Add the carrot, celery, onion, and a generous pinch of salt to the skillet. Cook, stirring occasionally, until the beef is cooked through and the vegetables are softened, 10 to 12 minutes. Stir in the wine and cook until evaporated, about 2 minutes. Stir in the water and cook, stirring occasionally, until the water is nearly evaporated, about 7 minutes. Season the filling with salt, then scrape into a 9-by-13-inch baking dish.
Drain the potatoes well and, using a paring knife, peel off the skins. In the same saucepan, melt the butter in the heavy cream over medium-low heat. Pass the peeled potatoes through a ricer or food mill into the saucepan. Season generously with salt and white pepper. Dollop the potatoes on the beef filling in the baking dish, then spread in an even layer. Bake for about 20 minutes, until lightly browned on top. Let stand for 5 minutes, then serve.