1/2 cup butter, softened
3/4 cup sugar
1 square unsweetened chocolate, melted and cooled
1 teaspoon pure vanilla
2 large eggs at room temperature

1 baked 9-inch pie shell

Cream butter; add sugar gradually.  Cream well; add cooled, melted chocolate and vanilla.  Blend well.  Add eggs one at a time, beating for five minutes after each egg.  Turn into pie shell and chill.  Top servings with whipped cream and sweet chocolate shavings.