Italian Potato Casserole

6 medium Russet potatoes, about 4 1/2 pounds
10 tablespoons butter, divided
1 cup seasoned bread crumbs, divided
1/2 cup whole milk
4 whole eggs
1 1/2 teaspoons kosher salt
1/2 teaspoon white pepper
3/4 cup freshly grated Parmesan cheese
1/4 cup freshly grated Romano cheese
1 teaspoon dry oregano
1 teaspoon dry basil
1 pound fresh mozzarella pearls (or a 1-pound ball cut into cubes)
1/2 pound Black Forest or Virginia ham sliced into quarter-inch slices then into one-inch pieces
1/4 pound sweet capocollo, sliced into quarter-inch slices then into one-inch pieces
1/4 pound soppresatta, sliced into quarter-inch slices then into one-inch pieces

Preheat oven to 350 degrees F.
In a 13x9x3-inch casserole dish, coat the bottom and sides with some of the butter then sprinkle in a couple tablespoons of the bread crumbs to coat the butter on the bottom of the casserole dish. Set the pan aside.
Peel the potatoes and cut each into quarters and place in a large pot of salted water. Bring to a boil and cook 20 minutes. Drain and place back in pan and turn on heat long enough to evaporate any residual water. It is OK if some of the potato pieces are not fully cooked through. The final dish will bake in the oven.
Use a potato ricer with large holes and rice the cooked potatoes into a large mixing bowl.
Add 6 tablespoons of the butter and mix to melt into the potatoes, then cool the potatoes completely while you prepare the remaining ingredients.
In a small bowl whisk the eggs and milk then add into the cooled potatoes.
Add the salt, pepper, Parmesan, Romano, oregano, basil, mozzarella pearls and all of the cut up Italian cold cuts.
Stir the mixture to combine then spoon into the prepared casserole dish, packing down as you add.
Sprinkle on the remaining bread crumbs then dot the top with the remaining butter and bake for 60 minutes or until browned and hot and bubbly. Place under the broiler for a few minutes to brown then let rest ten minutes.