According to Hennesy, the Master Blender's No 1 is
"The Hennessy Master Blender’s Selection Nº1 is a pure expression of unparalleled craftsmanship. Crafted as a single batch, it is the first in a series of rare and limited offerings.
Yann Fillioux, the 7th-generation Hennessy Master Blender is the conductor that brings a symphony of flavors into perfect harmony. For his passion project, the Hennessy Master Blender’s Selection Nº1, he has chosen eaux-de-vie at the peak of maturation — the perfect moment to be blended and bottled. Unlike other Cognacs, which strive for consistency over time, this blend is one-of-a-kind and will never be duplicated."
This is an extremely limited bottling, so if you're a fan of fine and unique cognac, do not hesitate to pick up a bottle of this.