This moist, fruity cake covered with rich pastry is traditionally eaten at Hogmanay. Make it in advance so the flavours have time to mature.
For the pastry, sift the flour into a bowl and rub in the lard and butter until the mixture resembles breadcrumbs. Add the salt, baking powder and water and mix to a soft dough. Turn out and knead into a ball. Wrap in clingfilm and chill while you make the filling.
Heat the oven to 180°C/160°C fan/350°F/Gas 4. In a large bowl, mix together the flour, raisins, currants, ginger, cinnamon, allspice, mixed spice, pepper, sugar, mixed peel, bicarbonate of soda, whisky, egg and buttermilk.
Line a 900g loaf tin with greaseproof paper. On a lightly floured surface, roll out two thirds of the pastry to a rectangle large enough to line the tin. Drape into the tin and press up against the sides. Spoon the filling into the tin, pressing down so it is dense.
Roll out three quarters of the remaining pastry to a rectangle large enough to cover the tin. Dampen the edges of the pastry with water and press the pastry lid on top to seal. Trim the edges. Crimp the edges using the tines of a fork. Roll out the remaining pastry with any trimmings, and use to make a bow to decorate the top, then attach with a little water.
Glaze with beaten egg and bake for 2 hours. Remove from the oven and leave to cool in the tin before turning out.