In medium saucepan, stir together sugar and cream of tartar until well combined. Add eggs and water beating until well blended. Add the chocolate squares. Cook over low heat, stirring constantly, until chocolate is melted and mixture reaches at least 160° F. Remove from heat. Stir in vanilla.

Set pan in bowl of ice water and stir vigorously until mixture is 80 to 90° F. Remove from ice water. Set aside.

In small mixing bowl at medium speed, beat butter until light and fluffy, about 3 to 4 minutes. Add cooled chocolate mixture. Beat at high speed 4 to 5 minutes.

Pour into pie shell.

Chill before serving, at least 6 hours.

Serve with whipped cream, almonds and shave chocolate.

Refrigerate any leftovers.