The Milanese buttonhole on Zegna cloth as done by Eric in the Wingtip Bespoke Basement.
You may be wondering why this is a big deal. When buttonholes are done by machine they are stitched first and then cut. However, hand worked buttonholes like this are cut first and then stitched. Therefore, there is no space for mistakes. It must be cut and stitched perfectly. Good job Eric!