Combine first 3 ingredients in a medium bowl, stirring with a whisk. Gradually add milk, stirring with a whisk. Set bowl over a saucepan of simmering water. Cook, stirring constantly, 8 minutes or until a thermometer registers 160°. Remove bowl from heat; add chocolate, vanilla, and, if desired, rum, stirring until chocolate melts and mixture is smooth.
Pour chocolate mixture evenly into 10 (4-ounce) ramekins or small glasses. Cover and chill 8 hours. Garnish with raspberries and mint, if desired.
Tip: Mixing in a splash of rum or brandy for adults adds a little touch of sophistication.
Kids Can Help: Kids can stir the chocolate with the help of a parent and watch it transform into this delicious dessert. They can also garnish the top with the raspberries and mint.