Scrub and de-beard the mussels, discarding any that are slightly open.
In a large pan sweat the onion and tomato in the wine, together with the bouquet garni and seasonings. Then add the mussels and heat them over a brisk heat for 5 minutes or so. As soon as the shells start to open, move the pan off the heat and start to remove the upper shell of each one. Place the mussels in their ha