Wash the mussels several times. Place in a bowl and cover with water. Place in the fridge and allow to soak for several hours, changing the water every hour or so.
Wash the mussels again and pull off the beards. If they had been soaked sufficiently, the beards should come off easily.
Place the mussels in a baking tray and pop in a preheated 180oC oven for about three minutes or just until the mussels partially open.
Let the mussels cool a bit, then break off the half shells, leaving the meat intact in the other half.
Arrange the half shells on a baking tray (a pizza dish was useful), dot with grated garlic (a toothpick is recommended), sprinkle with grated cheese and drizzle with olive oil liberally.
Put back in the hot oven and bake for about a minute or just until the cheese melts.