Cream shortening, 1 1/2 cups sugar and egg yolks until light. Add a few drops of milk if needed to cream sugar. Add chocolate and blend thoroughly. Sift flour with baking powder and salt. Add dry ingredients alternately with milk to chocolate mixture, blending well after each addition. Stir in vanilla and chopped nuts. Beat 2 egg whites until frothy. Gradually add remaining 1/2 cup sugar, beating until whites are stiff. Fold into batter. Turn into 2 greased and floured 9-inch layer cake pans. Bake at 350F 30 to 40 minutes, or until cake springs back when lightly touched with finger in center of cake. Cool slightly then remove layers from pans and cool completely on wire rack.

To make frosting, combine 3/4 cup sugar and brown sugar in heavy saucepan. Add hot water and cream of tartar and stir to blend. Cover pan and slowly bring to simmer. Uncover pan and cook until syrup spins long thin thread. Remove from heat. Beat 3 egg whites until stiff. When syrup stops bubbling, pour over beaten whites in thin stream, beating constantly until fluffy. Use to frost cooled layers. If desired, melt 1 ounce semisweet chocolate with 1/4 teaspoon butter and drizzle over frosting. Carefully swirl it over frosting with a thin spatula to give marbled effect.