In a saucepan cook the raisins in water 1 cup of water for 10 minutes. Drain the raisins, reserving ½ cup of water.
Preheat oven to 350ºF. Grease and lightly flour two 8 round cake pans.
In a large bowl, cream the sugar and butter until light and fluffy with an electric mixer on medium. Beat in the egg. In a small bowl sift together the flour, baking powder, salt, cinnamon, and allspice. Add to the creamed mixture alternately with the reserved raisin water. Stir in raisins and walnuts. Add the whiskey. Pour the batter into prepared pans and bake for 25 minutes or until pick inserted in center comes out clean. Cool the layers
In a small bowl, combine ¼ cup of butter, the confectioners sugar and vanilla. Add the whiskey a little at a time.
Place the first layer, top side down on a serving dish, frost with 1/3 of frosting. Place other layer top side up and use the frosting to coat the sides and top.