Make sure the canister of your ice cream machine has been in the freezer for at least 8 hours before preparing this recipe.
In a saucepan, combine cream, sugar, and cocoa powder. Bring to a low boil over medium heat, whisking to melt sugar and combine ingredients.
Once boiling, remove from heat and add chocolate, whisking to melt completely. Transfer to a larger container if needed, then whisk in milk, vanilla, and salt. Cover and chill for a minimum of 2 hours, but preferably longer.
When ready to churn, place the frozen canister in the machine. Remove the ice cream mixture from the freezer and pour it into the canister. Churn according to manufacturer's instructions.
Once mixed in and ice cream is churned, scoop into an airtight container and chill until solid.