In a large saucepan, combine milk and half-and-half; heat to 175°. Add chocolate, sugar and salt; stir until chocolate is melted and sugar is dissolved.
Remove from the heat. Cool quickly by placing pan in a bowl of ice water; stir for 2 minutes. Cool completely. Transfer to a large bowl; stir in the remaining ingredients. Cover and refrigerate for 30 minutes.
Fill cylinder of ice cream freezer two-thirds full; freeze according to the manufacturers directions. Refrigerate remaining mixture until ready to freeze, stirring before freezing each batch.
Allow to ripen in ice cream freezer or firm up in the refrigerator freezer for 2-4 hours before serving.