Beat 4 egg yolks until thick. In separate bowl combine egg whites, 1 teaspoon vanilla; beat until soft peaks form. Add 1/2 cup sugar, a little at a time until stiff peaks form. Fold yolks into egg whites. Add flour and walnuts. Fold carefully into egg white mixture. Spread batter into greased and floured pan. Bake at 375 degrees for 12 minutes.
Immediately loosen sides of cake. On a towel, sprinkled with confectioners sugar, carefully lift out and place cake. Starting at the narrow end, roll up cake and towel together. Let cool on rack. Whip heavy cream with 1/2 teaspoon vanilla and 1/4 cup sugar. Unroll cake and spread cream evenly. Roll cake and chill. Frost with chocolate glaze.
