You can save the unused egg whites and use them to make a meringue topping if desired.
Bring one cup of milk to a boiling point using the medium to medium-high heat. Grate chocolate and add to milk, stirring until blended. Add sugar and salt. Mix remaining milk gradually into the flour until smooth. Add the flour mixture slowly into the hot milk mixture, blending well. Beat egg yolks until they are thick. Add a small amount of the hot mixture into the yolks and then add the warmed yolks into the hot mixture. Cook mixture, stirring constantly until thickened. Remove from heat. Add butter and vanilla. Pour into prepared pie shell.
0 servings