From food writer Michele Scicolone: My dad didn't cook all the time, but when company was coming, he liked to pitch in. One year he decided to try to duplicate a dish that his mother used to make -- a casserole of potatoes mashed with mozzarella, prosciutto, and salami and baked until the cheese melted and the top was crusty and browned. From the first bite, we loved this dish. We ate it as a side with chicken or a roast, and on its own with a green salad.
Place the potatoes in a large saucepan with cold water covering them completely. Cover the pan and bring the water to a simmer over medium-high heat. Cook the potatoes until they are tender when pierced with a knife, about 20 to 30 minutes. Drain them and let them cool slightly.
Generously butter a 2-quart baking dish. Sprinkle the dish with the bread crumbs, turning it to spread the crumbs evenly.
When the potatoes are cool enough to handle, remove the skins. Place the potatoes in a bowl and mash them until smooth. Stir in 3 tablespoons of the butter, the milk, 1 cup of the grated cheese, the egg, the nutmeg, and salt and pepper to taste. Fold in the mozzarella and meat.
Heat the oven to 400º. Spread the mixture evenly in the dish, dot with the remaining 1 tablespoon of butter, and sprinkle with the remaining 2 tablespoons of grated cheese. (This dish can be prepared to this point and refrigerated for up to 24 hours.)
Bake the dish until the top is browned and the center is hot, 40 to 45 minutes (50 minutes if it was refrigerated). Let it cool for 10 minutes before serving. Serves 10.