Heat dairy mixture on medium-low and cook, whisking constantly, until mixture thickens and reaches 180°F. Remove from heat and mix in chocolate chips, stirring until fully melted. Add salt to taste, then pour into a medium-sized bowl. Cover with cling wrap, pushing it all the way down so that it touches the surface of the ice cream base to prevent a skin from forming. Chill for at least 8 hours or overnight in the refrigerator.