About 30 minutes before the panettone have fully risen in the panettone papers, preheat the oven to 400°F.
Make sure your oven rack is placed on a low enough shelf to allow you to fit the panettone in the oven.
Remove the clingfilm and let the panettone surface dry out and form a crust (about five minutes) so you can make a crisscross incision on the surface of the panettone.
Use a buttered razor blade or very sharp buttered knife.
Make the incision very carefully as you don't want to deflate the panettone.
Place a tablespoon nut of butter in the center of the criss cross.
Place the panettone in the oven, along with a cup of hot water, and bake for 10 minutes.
Reduce the temperature to 350°F and bake for an additional 10 minutes.
Lower the temperature to 325°F and bake until the panettone are golden brown and a wooden barbecue stick inserted into the center of the panettone comes out clean, approximately 30 minutes.
An instant read thermometer inserted into the panettone will read about 195°F.
Midway through baking you may need to place a sheet of tinfoil lightly atop each panettone if you see they have already baked to a golden brown.