Reduce oven temperature to 350°F.
To the bowl with the potato centers, add butter, ham, 1 cup mozzarella cheese, cream cheese, sour cream, chives, ranch seasoning, salt, and pepper.
Mash until smooth and well combined.
Spoon the filling evenly into the potato shells.
Top with the remaining mozzarella cheese.
Bake for 15 to 20 minutes, until heated through and the cheese is melted.
Remove from oven and top with diced pickles.
Serve warm with sour cream, if desired.