1 c. butter
1 1/2 c. sugar
4 sq. unsweetened chocolate
1 tsp. vanilla
4 eggs
1 (9 inch) frozen pie shell
Cool Whip

Prepare pie shell according to directions on package. Melt chocolate in saucepan. Set aside to cool thoroughly. Beat butter and sugar until smooth and creamy. Add cooled chocolate and vanilla. Beat mixture on medium speed approximately 2 minutes.

Add first egg; beat on medium 5 minutes. Add second egg; beat on medium 5 minutes. Do the same for the third and fourth eggs. Pour mixture into cooled pie shell. Chill pie in refrigerator at least 4 hours. Top each slice of pie with a tablespoon of Cool Whip.