I don’t know what source it could be. Maybe the “Journal of Making Of Empire” book by Alan Arnold, or the later “Making Of Empire” book by JW Rinzler?
Both those have a number of quotes from Kershner on Empire, but it could also be something obscure like a Starlog or Insider article?
It’d certainly been cool to hear Kershner’s take, input and contributions to the force in the Empire Strikes Back!