This can be used as a base for ice cream or consumed on its own.
Vanilla Bean, Split in half
Combine milk and cream in a medium saucepan. Scrape in seeds from vanilla bean and add bean.
Bring milk mixture to 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).
Strain sauce into bowl. Cover and chill.
Remember that this is just a base for the ice cream, if you plan on using it.