Serve with thin slices of whole-grain bread and mustard sauce (recipe below). (The gravlax will keep in the refrigerator for a week if well wrapped in foil and plastic, and in the freezer for two ...

Stir in the wholegrain mustard ... the sauce can be prepared up to two days in advance. If you want to get ahead, carve the cold beef an hour or two before serving then reassemble as a whole ...