salt in a medium saucepan. Add milk, and cook over medium heat, stirring constantly, until candy thermometer registers 170°. Remove mixture from heat, and stir in melted chocolate. Cool.
Place egg yolks in top of a double boiler, and beat slightly. Slowly add chocolate mixture to beaten egg yolks, stirring constantly. Cook over boiling water, stirring constantly, until mixture thickens and is smooth. Remove from heat, and stir in vanilla.
Spoon mixture into four individual dessert bowls. Cool to room temperature. Cover and chill thoroughly. Sprinkle with grated chocolate, if desired.