Chop chocolate. In a 1 1/2-quart saucepan bring cream, milk, sugar, and salt just to a boil over moderate heat, stirring, and add chocolate and butter. Reduce heat to low and cook mixture, stirring, until chocolate is melted and mixture is smooth.
Ladle hot chocolate into demitasse cups and top with whipped cream and a few raspberries (raspberries will sink to the bottom).
