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 heat.
Quickly transfer to a large bowl; place bowl in a pan of ice water. Stir gently and occasionally for 2 minutes. Stir in remaining ingredients. Press plastic wrap onto surface of custard. Cover and refrigerate for 30 minutes.
Fill cylinder of ice cream freezer two-thirds full; freeze according to the manufacturer’s directions. (Refrigerate remaining mixture until ready to freeze.) Transfer ice cream to freezer containers, allowing headspace for expansion. Freeze 2-4 hours or until firm. Repeat with remaining ice cream mixture.Yield: about 4-1/2 quarts.