Cream butter and sweetener until completely smooth.
Add chocolate and vanilla.
Beat in eggs, one at a time, beating 5 minutes after each addition.
Turn into cooled pie shell.
Decorate with whipped cream before serving, if desired.
Per Serving: 313 Calories; 33g Fat (89.1% calories from fat); 4g Protein; 5g Carbohydrate; 2g Dietary Fiber; 156mg Cholesterol; 264mg Sodium.