Grease the baking sheet with butter.
To make the pastry sift the flour and salt into the mixing bowl or food processor bowl.
Add the butter and lard and then rub it in (or process if using a food processor) until the mixture resembles fine breadcrumbs.
Place the egg yolk in a cup, add the ice cold water and whisk together.
Add to the pastry mix and bring together to make a dough adding more water if the dough is too dry. If using a processor add the egg mixture and whizz until the mixture forms a ball of dough.
Wrap the dough in clingfilm and place in the fridge for half an hour.
Meanwhile place the butter into the medium mixing bowl, add the chopped ginger and currants and mix until evenly incorporated.
Take the pastry out of the fridge and allow to come to room temperature.
Roll out a third of the pastry into a rectangle slightly larger than the salmon and place on the greased baking sheet.
Place one fillet onto the pastry and spread half the butter, ginger and currant mixture over the top of it. Place the second piece of salmon over the first one and spread the rest of the butter, ginger and currant mixture over the top.
Brush the edges of the pastry base with beaten egg.
Roll out the rest of the pastry and place carefully over the salmon and seal onto the pastry base by crimping either with your finger, the handle of a wooden spoon or a fork. Trim round the base so you have a neat edge.
Make a hole in the centre of the top of the pastry to allow any steam to escape. Decorate with shapes made from any left-over pieces of pastry which can be stuck down using beaten egg.
Place the ‘pie’ in the fridge and leave to rest for an hour.
Preheat the oven to 180C/350F/gas 4.
Take the ‘pie’ out of the fridge and brush the pastry with the beaten egg and place in the oven and bake for 40 to 50 minutes.
After 30 minutes check that the top of the ‘pie’ isn't burning. If it is, place a sheet of foil over the top and continue to bake.
Meanwhile make the Sauce Messine: Wash the herbs and pick the leaves off the stalks then chop finely.
Place the egg yolk, cream, mustard and lemon juice in the top of the double boiler or in the heat-proof bowl and whisk together thoroughly.
Heat water in the bottom of the double boiler or a saucepan and bring to a gentle simmer.
Place the top of the double boiler or heat-proof bowl over the water and heat, stirring continuously until slightly thickened.
Place the herbs, onion and seasoning in the sauce and continue stirring for a further 5 minutes.
Remove the ‘pie’ from the oven and carefully slide it onto a serving dish. Serve immediately with a jug of the sauce messine.
