Sift flour, baking powder, cocoa, and salt together. Add nuts and mix well. Add sugar gradually to eggs, beating constantly. Blend in shortening. Add flour - nut mixture and beat thoroughly. Add vanilla. Pour into a greased and floured 8 x 8 baking pan. Bake at 350 F for 30 to 35 minutes. Cool and turn out of pan. Cut into squares.
