Place all the raisins in a small bowl with rum. Let soak overnight, if possible.
Preheat oven to 190 C / Gas 5. Grease and flour one 20x30cm or similar sized baking tin.
In a large bowl, cream the butter and sugar together. Beat in the eggs, then the apple sauce.
In another bowl, stir together the flours, cornflour, bicarbonate of soda, spices, salt and cocoa. Beat into the creamed ingredients. Stir in the raisins, leftover rum and the walnuts. Pour batter into the prepared tin.
Bake at 190 C / Gas 5 for 25 minutes or until cake tests done. Let cool on a rack.