Feigin-Frenkel duality is the isomorphism between the principal W-algebras of a simple Lie algebra g and its Langlands dual Lie algebra L g. A generalization of this duality to a larger family of W-algebras called hook-type was recently conjectured by Gaiotto and Rapčák and proved by the first two authors. It says that the affine cosets of two different hook-type W-algebras are isomorphic. A natural question is whether the duality between affine cosets can be enhanced to a duality between the full W-algebras. There is a convolution operation that maps a hook-type W-algebra W to a certain relative semi-infinite cohomology of W tensored with a suitable kernel VOA. The first two authors conjectured previously that this cohomology is isomorphic to the Feigin-Frenkel dual hook-type W-algebra. Our main result is a proof of this conjecture.