Place 1 cup chopped walnuts in boiling water 3 to 5 minutes; drain well, and set aside.
Cream shortening; gradually add sugar, beating well. Add egg yolks; beat well.
Combine 2 3/4 cups flour, baking powder, salt, and spices; mix well. Add flour mixture to creamed mixture alternately with milk, beginning and ending with flour mixture. Mix well after each addition. Dredge black walnuts in remaining 1/2 cup flour; fold into batter. Beat egg whites (at room temperature) until stiff peaks form; fold into batter.
Pour batter into 3 greased and floured 8 - inch square cake pans. Bake at 350° for 25 to 30 minutes or until a wooden pick inserted in center comes out clean. Cool in pans 10 minutes; remove layers from pans, and let cool completely. Spread Buttery Cinnamon Frosting between layers and on top and sides of cake. Garnish with additional chopped walnuts.