Place chocolate in a small, heavy saucepan; cook over low heat until chocolate melts.
Set aside to cool.
Cream butter; gradually add sugar, beating at low speed of an electric mixer until light and fluffy.
Add eggs, one at a time, beating well after each addition.
Add chocolate and flavorings; mix well.
Combine vanilla wafer crumbs and pecans; stir well.
Sprinkle half of crumb mixture into 12 ungreased muffin cups.
Spoon chocolate mixture over crumb mixture, and top with remaining crumb mixture.
Cover and freeze until firm.