How can you become a Buddha by doing zazen?

*     *     *

When Baso was living in Demboin, he did zazen (sitting meditation) every day. Nangaku, realizing Baso was a ‘vessel of the Law’ (one who would become an exemplary Enlightened being and teacher), went and asked him, “Sir, what is your idea in doing zazen?”

“I intend to become (a) Buddha”, Baso replied.

Nangaku picked up a tile and began polishing it in front of the hermitage. Baso asked, “What are you doing?” Nangaku answered, “Polishing it to make it into a mirror.” “How can you make a mirror by polishing a tile?” demanded Baso.

“How can you become a Buddha by doing zazen?” retorted Nangaku.

*     *     *

Nangaku’s point here is that everyone already has Buddha nature inherently; and that no amount of any particular practice, study, method or wordplay will make one become what one already is. Only realization solves the conundrum.  -What conundrum?!