Preheat the oven to 180C/350F/Gas 4 and grease and line a 2lb (1kg) loaf tin.
This is a two part process so make the pastry first by sifting the dry ingredients into a large bowl and rubbing in the butter. It is best to chop the butter into tiny pieces and rub in with just the finger tips. Add iced water to form a stiff dough. Wrap in clingfilm and chill for 30 minutes. Flour your work surface and roll the pastry thinly. Press this into the tin ensuring it is evenly distributed, make sure that you have enough left over to make the lid for the top!
Now on to stage 2, the easy bit; To make the cake filling simply put all the dry ingredients into a large bowl and mix thoroughly, stir in the eggs and whisky and add enough milk to bind it all together.
Pack it into the pastry case and level off the top. Cover with the remaining pastry to form a lid and seal all edges firmly together. Prick all over with a fork and brush with the egg yolk to glaze.
Bake for 2 hours at the full heat and then reduce the oven temperature to 140C/275F/Gas 1 and bake for a further 1 hour until the top is golden.
Let it cool before turning out of the tin.