Grease and flour two 8x1-1/2-inch or 9x1-1/2-inch round cake pans; set aside. In a medium mixing bowl beat together the 1/2 cup sugar and shortening with an electric mixer on medium speed until fluffy. Add egg yolks, one at a time, beating 1 minute after each addition. Add vanilla. Stir together flour, baking powder, and salt. Alternately add flour mixture and milk to egg mixture, beating on low speed after each addition until combined. Spread evenly into prepared pans; set aside.
For the meringue, in a large mixing bowl beat egg whites and cream of tartar until soft peaks form (tips curl). Gradually add the 1 cup sugar, beating until stiff peaks form (tips stand straight). By hand, fold in walnuts. Spread meringue evenly over batter in pans. Bake in a 350 degree F oven for 30 to 35 minutes or until a toothpick inserted in center comes out clean. Cool 10 minutes. Carefully loosen cakes from pans; invert pans to remove cakes. Cool cakes completely, meringue side up, on wire racks.
For chocolate whip, in medium mixing bowl combine the 3/4 cup sugar and cocoa powder. Gradually stir in whipping cream. Beat just until soft peaks form. Place a cake layer on a serving plate. Spread half of the chocolate whip over layer. Top with second cake layer; spread top with remaining chocolate whip. Cover loosely. Chill 30 minutes or up to 6 hours. Makes 10 to 12 servings.