Scrub and pick through the mussels pulling off the beards and discarding any that are broken or that dont close when tapped, tip into a pan with a splash of boiling water and cover with a tight fitting lid, cook over a high heat for 2 minutes and then pour into a large colander and leave until cooled.
In a small pan soften the shallots in 25g of butter and then pour in the Martini. Cook until it has evaporated and then scrape the shallot into a mixing bowl
To make the stuffing, combine the remaining ingredients with the shallots and season with plenty of freshly ground black pepper.
Remove and discard the top shell of the mussels and arrange on a large baking tray scatterd generously with rock salt to keep the mussels stable, add a teaspoon full of the stuffing into each shell and place under the grill for 2-3 minutes until golden and bubbling.