Ingredients 5 lbs of potatoes (2.200 grams) do not use new potatoes 1 1/4 stick butter (6 ounces or 140 grams) 4 extra-large eggs room temperature 1 cup milk at room (240 ml)temperature 2/3 cup Parmigiano Reggiano or Pecorino Romano 1 lb mozzarella cut in cubes (453 grams)