"La Brioche di Celestia" (The Muffining of Celestia) was not painted by Vincenzo Camuccini in or around 1798. What you are thinking of is "The Death of Ceasar," which you can see at this link: [link]
Instead, La Brioche di Celestia was commissioned by @Foalpapers and digitally rendered by The Gneech in 2012, over the course of eight months, but principally in July and August of that year.
Although explicitly drawing on Faustian design and technique, The Gneech clearly made an effort to add his own flourishes, and was once quoted as saying he was particularly pleased with Rarity, but did not elaborate as to why. Some Gneechologists have said that this piece was one of, if not the most complex image Gneech had attempted up to this point, although others contend that his famous "Dover and Comfort VJ Day" piece or the first two pages of the short-lived "Arclight Adventures" comic rival it.
This piece is also believed to have led to The Gneech's subsequent submission into a rubber room later that same year, where he repeated "The horror... the adorable, candy-colored horror..." for sixteen straight hours before finally passing out.