Combine
sugar, milk, salt, and cocoa powder in a saucepan over medium heat,
stirring constantly. Bring to a simmer. Place the egg yolks into a small
bowl. Gradually stir in about 1/2 cup of the hot liquid. and return to
the saucepan. Heat until thickened, but do not boil. Remove from the
heat, and stir in the chopped chocolate until chocolate is melted. Pour
into a chilled bowl, and refrigerate for about two hours until cold,
stirring occasionally.
When
chocolate mixture has completely cooled, stir in the cream, and vanilla.
Pour into an ice cream maker, and freeze according to manufacturer's
directions.
