Combine milk and cream in heavy medium saucepan and bring to a simmer. Remove from heat.
Whisk egg yolks and sugar in medium bowl to blend. Gradually whisk hot milk mixture into yolk mixture. Return custard to saucepan. Stir over low heat until custard thickens and leaves path on back of spoon when finger is drawn across, about 5 minutes (do not boil). A thermometer should reach 180°F. Strain the mixture into a bowl set over an ice water bath. Stir in the vanilla extract.