Boil the potatoes until fork tender and let cool.
Add an egg, the cooked onions and pancetta, the grated Parmigiano cheese, Parmigiano chunks and salt, and black pepper, to taste. Mix well until all the ingredients are evenly distributed.
Transfer the potato mixture to the baking dish and spread the mixture evenly over the pan, packing the mixture so it serves as a solid bed. Add the remaining bread crumbs on top. Bake for 20 minutes or until the bread crumbs are golden brown.