In a saucepan, bring milk to a simmer over medium-high heat, stirring frequently. Stir in cocoa nibs and salt, cover with plastic wrap, and let steep for 2 hours. (this step can be done the day before then left in the fridge overnight)
In a clean saucepan, whisk together sugar and cocoa powder until no large lumps of cocoa remain. Then whisk in egg yolks until thoroughly combined.
Strain milk into yolk mixture, pressing on cocoa nibs to squeeze out all possible dairy, then whisk dairy to combine. Set pan over medium heat and cook, whisking frequently, until custard reaches 170°F on an instant-read thermometer. Custard should coat the back of a spoon and a finger swiped across it should leave a clean line.
Add chocolate and stir until thoroughly melted. Strain into a large measuring cup or bowl, and chill in refrigerator or ice bath until base cools to 40°F. Churn in ice cream maker according to manufacturer’s instructions, then serve.
The most decadent, dark chocolate ice cream you will ever have!