In a large nonreactive saucepan over medium heat, combine the milk, heavy cream, sugar, and chocolate chips. Whisk until the sugar is dissolved and the chocolate melts completely. Heat the mixture to the scalding point (when bubbles form around the edges of the pan). Remove from the heat.
Beat the egg yolks in a large mixing bowl. Add the cream mixture, about 1/4 cup at a time, to the beaten egg, whisking well between each addition, until it is all used. Pour the mixture back into the saucepan and cook, stirring, over medium heat until the mixture becomes thick enough to lightly coat the back of a spoon, 2 to 3 minutes.
Remove from the heat and strain through a fine-mesh strainer into a glass bowl. Cover the top of the mixture with plastic wrap (this keeps a skin from forming) and keep cool. Place the mixture in the refrigerator and chill completely.
Pour the mixture into the ice cream machine and follow the manufacture’s instructions for the churning time.
Yield: 1/2 gallon