Boil the potatoes until fork tender. Set aside to cool slightly.
In the meantime, cook your sausage meat, and set aside.
Dice the ham and shred the mozzarella.
Once cool enough to handle, peel and rice the potatoes.
Add in unsalted butter, salt (not too much salt because the add ins are salty), pepper, eggs and milk and mix well.
Add in ham, sausage, mozzarella, grated cheese.
Mix until thoroughly combined.
Butter a 12 inch round pan or 9x12 baking dish, sprinkle with plain breadcrumbs to coat.
Place the mixture into the pan and then top with more plain breadcrumbs and a few pats of butter.
Bake at 375°F for 1 hour or until golden brown on top.
Allow it to cool and set for at least 20 minutes before serving.
