If time is available, let herb steep in milk overnight. Strain out herbs and vanilla bean and heat with sugar. Bring to scalding.
Hand whisk the yolks in a stainless steel bowl.
Temper the yolks by adding only a ladle of hot milk to the yolks. Mix well then add tempered yolks back to the saucepan. On medium heat, whisk constantly for 2 minutes. Strain and cool in an ice bath. When mixture is cooled, add heavy cream.