Many gourmands, supposed gourmands have never tried it. It is one of those parts that you keep for yourself, a finger removes it by a swift push underside the skeleton, or this part of the chicken gets overlooked.

French sot-l’y-laisse translates roughly to “the fool leaves it there”, as any unskilled carvers accidentally leave it on the skeleton. The sot-l’y-laisse is also referred to as the “chicken oyster”, a part of the chicken that also looks like an oyster. In the photo above the two small grape like pieces are the sot-l’y-laisse. It’s slightly dark meat is recognized as the sweetest meat on the chicken, firm but tender and juicy. Located right on the saddle, right and left adjacent to the thigh, many gourmets consider it to be the best part of the chicken. I do too.

http://www.cooking2000.com/fr/dossier/decouper-la-volaille.htm