1 Preheat oven to 325 degrees F (165 degrees C). Grease and flour a 9×13 inch pan. Sift together the flour, baking powder, salt, cinnamon and allspice. Set aside.
2 In the top of a double boiler, heat chocolate, stirring occasionally, until chocolate is melted and smooth. Remove from heat and allow to cool to lukewarm.
3 In a large bowl, cream together the shortening and sugar until light and fluffy. Beat in the egg yolks one at a time, then stir in the vanilla. Beat in the flour mixture alternately with the milk. Stir in walnuts.
4 In a large glass or metal mixing bowl, beat egg whites until stiff peaks form. Fold 1/3 of the whites into the batter, then quickly fold in remaining whites until no streaks remain. Pour batter into prepared pan.
5 Bake in the preheated oven for 45 to 50 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow to cool.