Melt the unsweetened chocolate and butter in top of double boiler over hot water (or in microwave). Cool slightly.
Gradually add sugar to eggs, beating thoroughly after each addition. Blend in chocolate mixture. Stir in flour. Add vanilla, half the nuts, and half the semisweet chocolate pieces.
Spread in greased 9-inch square pan. Sprinkle remaining chocolate pieces and nuts over batter.
Bake at 325 degrees for 30 minutes.
Remove and cool in pan. Cut in squares.
Recipe submitted by ~Donna~ V on 7/23/98