Mussels Gratin (Cozze al Gratin)

INGREDIENTS
1 Kg. Black fresh mussels
Breadcrumbs
Chopped parsley
Extra virgin olive oil
Salt and pepper

Clean the mussels
Select the mussels, never choose a mussel chiappe, broken or damaged. Just before cooking, soak your mussels in fresh water. Soak them for about 20 minutes. As the mussels breathe, they filter water and expel sand. After about 20 minutes, the mussels will have less salt and sand stored inside of their shells.
To remove the beard, using a dry towel, grasp the beard and give a sharp yank out and toward the hinge end of the mussel.
Place these mussels into another bowl full of clean cold water.
Once the mussels have been soaked, use a firm brush to brush off any additional sand, barnacles, or other oceanic attachments. Rinse the mussels under cool tap water, and set aside. Dry with a towel before cooking.
Preparation
Remove the upper shell, leaving the mussel attached to the bottom shell.
In a large baking pan pour few tablespoons of salted water, fill each with breadcrumbs, chopped parsley, olive oil, salt and pepper and place them to the pan.
Bake in oven to 200 C for 15 minutes.
Once baked, season with salt and pepper and serve.