Heat the heavy cream, milk, vanilla bean and espresso in a large, heavy-bottomed saucepan over medium heat. Place the egg yolks and sugar in a heatproof mixing bowl and beat until pale yellow in color and all of the sugar has dissolved. Temper about 1/2 a cup of the cream mixture into the egg mixture and whisk vigorously to incorporate well. Add the egg mixture to the saucepan with the cream mixture and cook, stirring constantly with a whisk, or wooden spoon. Be sure to stir in the corners of the pot and lower the heat slightly. Stir the pot for 4 to 5 minutes or until the custard has thickened enough to coat the back of a spoon.

Remove from the stove and strain the custard through a fine mesh sieve into a clean bowl. Place the bowl in another bowl half-filled with ice and water to cool the custard. To chill the custard faster, stir it occasionally with a spoon. Pour the chilled custard into an ice cream machine. Churn according to the manufacturer's instructions, and fold the chocolate chips into the partially frozen custard. Pack into an airtight container and freeze until ready to serve.