French Silk Pie

Directions

1. 1
   Mix sugar and butter until smooth. Melt chocolate and let cool.
2. 2
   Add cooled chocolate to sugar and butter mixture; blend until smooth. Add vanilla and cream of tartar, mix well.
3. 3
   Beat in eggs, one at a time, mixing well between each addition.
4. 4
   Mix until smooth.
5. 5
   Pour into pie shell.
6. 6
   Chill until firm.
7. 7
   Top with whipped cream.