How to Make It
In a small saucepan, heat the milk and cream with the vanilla. In a large bowl, whisk the egg yolks with the sugar until light and foamy, about 3 minutes. Whisking constantly, pour the hot milk mixture into the egg yolks in a thin stream.
Return the custard to the saucepan and cook over moderately low heat, whisking constantly, until thickened, about 5 minutes; do not let the custard boil or it will curdle. Immediately scrape the sauce into a clean bowl and whisk constantly to cool slightly. Set the Vanilla Custard Sauce aside to cool completely, then refrigerate until ready to use.