Cream butter; add sugar gradually, creaming well. Blend in cooled, melted chocolate. Add vanilla extract. Add eggs, one at a time, beating 5 MINUTES after each addition. Turn filling into cooled shell. Chill pie in freezer for 10 minutes, then in the refrigerator for 1 to 2 hours before serving.
If desired, serve garnished with whipped cream and chopped nuts.
