
Pre-heat the oven to 180 C°/350 F°.
Peel, steam and mash the potatoes (a potato ricer does the best job), beat them with a wooden spoon until they are completely smooth.
Add the butter, Parmesan, Pecorino, eggs+yolk, the salame or ham, parsley, salt, pepper. Add a little milk if the mash looks too stiff.
Pour a little more than half into the tin, without dislodging the breadcrumbs.
Use the palm of your hands to press the mix in place: try to have some potato mix also up the wall of the tin.
Add the mozzarella and the scamorza and cover with the remaining potato mix.
Scatter the top with breadcrumbs and cover with slivers of butter.
Bake in the oven for about 45 minutes or until the gattò looks deep golden and is bubbling.
Remove from the oven and let it rest for half an hour before eating, loosely covered with tinfoil.