Sift flour once, measure, add cocoa, baking powder and salt and sift together three times. Cream butter thoroughly, add sugar gradually, and cream together until light and fluffy; then beat in egg. Add flour, alternately with coffee, a small amount at a time, beating after each addition until smooth. Add vanilla. Bake in two greased 9" layer pans in moderate oven, 375~, 30 minutes. Cool. Add confectioners' sugar to whipped cream, mixing until blended. Fold dates and nut meats into whipped cream. Spread between layers of cake. Sift confectioners' sugar over top of cake.