Season the salmon fillets well on both sides with salt. Mix the softened butter with the stem ginger, currants, mace, 1/2 teaspoon of salt and some black pepper. Spread the inner face of 1 salmon fillet evenly with the butter mixture and then lay the second fillet on top.

Cut the pastry in half and, on a lightly floured surface, roll out 1 piece into a rectangle about 4 cm bigger than the salmon all the way around ~ approximately 18 x 33 cm. Roll out the second piece into a rectangle 5 cm larger than the first one all the way round.

Lay the smaller rectangle of pastry on a well-floured baking sheet and place the salmon in the centre. Brush a wide band of beaten egg around the salmon and lay the second piece of pastry on top, taking care not to stretch it. Press the pastry tightly around the outside of the salmon, trying to ensure that you have not trapped in too much air, and then press the edges together well.

Trim the edges of the pastry neatly to leave a 2.5 cm band all the way around. Brush this once more with egg. Mark the edge with a fork and decorate the top with a fish scale effect by pressing an upturned teaspoon gently into the pastry, working in rows down the length of the parcel. Chill for at least an hour.

Pre—heat the oven to 200°C and put in a large baking sheet to heat up. Remove the salmon en croute from the fridge and brush it all over with beaten egg.

Take the hot baking sheet out of the oven and carefully transfer the salmon parcel on to it. Return it to the oven and bake for 35-40 minutes.

Remove the salmon from the oven and leave it to rest for 5 minutes. Transfer it to a warmed serving plate and take it to the table whole. Cut it across into slices to serve.