In a saucepan over medium heat, combine the milk, cocoa powder, salt, and half the sugar. Stir the mixture constantly as you bring it just to a simmer. Remove from heat.
In a small bowl, whisk together the egg yolks and sugar just until combined.
To temper the eggs, slowly add 1/2 cup of the chocolate mixture in a drizzle into the egg mixture. Do this slowly so as not to cook the eggs.
Pour the entire egg mixture back into the saucepan with the chocolate mixture. Heat over medium heat until thickened, about 3-5 minutes. Do not boil the mixture.
Remove the pot from the heat and add in half of the chopped chocolate, stirring until chocolate is melted.
Pour the mixture into a chilled bowl and refrigerate for about two hours until cold. To avoid putting the hot mixture in the refrigerator, you can chill the bowl over another bowl filled with ice for 10-15 minutes to cool it down first.
After the chocolate mixture has completely cooled, stir in the cream and vanilla. Pour the mixture into your ice cream maker, and freeze according to the manufacturer's directions. After 2-3 minutes, add the remaining chopped chocolate so it can blend into the ice cream.