In small saucepan, place 1/2 cup whipping cream, semisweet and unsweetened chocolate chunks. Heat over medium low heat until chocolate melts, stirring frequently. Remove from heat; set aside. (I have done this in the microwave on 70% power stirring after a minute and then every 20-30 seconds thereafter.).
In medium saucepan over medium heat, heat half and half until very hot but not boiling, stirring often. Remove from heat; set aside. (I've also done this in the microwave for about a minute.).
In small bowl, combine sugar and cocoa powder; set aside. Place egg yolks in mixer bowl and beat; gradually add sugar mixture and mix about 30 seconds or until well blended and slightly thickened. Very gradually add chocolate mixture and half and half; mix until well blended.
Return half and half mixture to medium saucepan; stirring constantly, cook over medium heat until small bubbles form around edge and mixture is steamy. Do not boil. Transfer half and half mixture into large bowl; stir in remaining 1-1/2 cups whipping cream, vanilla, and salt. Cover and chill thoroughly, at least 8 hours (I chill mine in the freezer for 2 hours, stirring after 1st hour and then every 15 minutes until 2 hours.).
Put the mixture into your ice cream maker and let it go to work. :) During the last 1-2 minutes of freeze time, add in the milk chocolate. Immediately transfer ice cream into serving dishes or freeze in airtight container. Enjoy!