Combine egg yolks and sugar in small bowl until smooth and lemon colored. Place cream, milk and vanilla bean in small saucepan over medium heat and bring to boil. Immediately remove from heat and cool slightly. Remove vanilla bean and add a small amount of cream to the yolks, stirring briskly. Slowly add yolks to remianing cream, stirring constantly. Strain through cheesecloth or a fine sieve. Melt chocolate over hot water in the top half of a double boiler or in the microwave. Stir into cream mixture and strain once more. Stir in whiskey and chill. When well chilled, pour into an ice cream maker. Makes about 1 1/2 quarts.