Currently for sale at $100 via AbeBooks, Science-Fantasy Correspondent #2 (1937). Containing Bloch’s story “A Visit with H. P. Lovecraft”.
Joshi’s bibliography lists it as “fictional reminiscence” re: its reprint in the book Lovecraft At Last, and comments elsewhere reveal it to be a “hilarious” bit of humorous writing. A little further digging reveals it to have been reprinted more recently in the appendix of H.P. Lovecraft: Letters to Robert Bloch and Others.
An earlier and fuller sales listing for the original zine has found its way to the Amazon description, and this notes…
In the story, Lovecraft is depicted as eating the writer of the story. Lovecraft comments separately “…I seldom eat people alive except for Sunday dinner. As a general thing, I prefer human flesh cooked; and I generally avoid authors as a diet, since they tend to be lean and tasteless.”
Regrettably the story/zine is not scanned and on Archive.org or in the Hevelin online collection. I imagine a crowd-funder for a comics adaptation of it might do rather well.