Preparation

Whisk egg yolks and sugar in medium bowl until well blended, about 2 minutes. Bring milk and vanilla bean to boil in heavy medium saucepan; gradually whisk into yolk mixture. Return custard to saucepan and stir over medium heat until custard thickens and leaves path on back of spoon when finger is drawn across, about 4 minutes (do not boil). Transfer to bowl. Cover and refrigerate until cold. (Can be prepared 1 day ahead. Keep refrigerated.)