As far as I know, in the last several years, the only comic Mike Mignola supplied the cover art as well as the interior art for was Hellboy: In the Chapel of Moloch. This makes it worth the effort of skimming through back issue bins at comic book shops for. Granted, all of the artists who work on Hellboy are good, but nothing quite compares with the series’ creator taking over the art. When the series first began, all of the art was by Mignola (with Dave Stewart supplying colors). This meant, for one thing, the reader could watch as Mignola’s style improved (compare the art from the first issue to the art that came in the later Strange Places arc), but it also meant it took a long time for new issues to come out, especially with Mignola taking on other projects like BPRD and Witchfinder. So, of course, we fans can understand why he hired other illustrators.
What’s funny about this issue is that Mignola weaves in a metafictional story where Hellboy is sent to Portugal to find an artist who hasn’t been seen for a long time, likely an in-joke aimed at Mignola himself. The fictional artist does work inspired by Goya, and on the cover, if you look closely, it’s inscribed “After Goya.”