I am writing on behalf of a friend who is reading Invitation to a Beheading. He came across the term "fried chuckrick" and could not find a definition. I always assumed that it was a made-up word meant to convey something folksy-crude and fried (something like "ponchiki", I imagined), but there have been others who assumed VN made up words, only to be shamed by his unabridged dictionary, so now I wonder... (I don't have Dal' handy.)
I do have Dal' handy and it defines "Khukhrik" or "huhrik" ( in VN's transliteration) as a dialectical word meaning "shchegolek. i.e., a "fop" or "dandy"--which doesn't get us very far. "Shchegolek," however, comes from the (possibly different) root(s) shchegOl-/shchOgol' (the
capital "O's" = stress), the first, "shchegOl" now meaning the "Eurasian Goldfinch" (Carduelis carduelis) and the latter, "shchOgol'" a "Spotted Redshank," (Tringa erythropus) related to snipe and woodcock. Both are common in Northern Europe. (On my bird life list as Goldfinch: Lagos, Portugal 10 Dec. 1978 & Spotted Redshanks: Minsmere, England Jun 10, 1992). Small passerines like sparrows (or finchs?) are roasted and eated in Spain, but I have not seen them consumed elsewhere in Europe; nor do I know whether "Spotten Redshanks" are eaten although their kinship with snipe and woodcock suggests that such might be the case. So, to conclude: my guess is that Nabokov's characters are eating a game bird resembling a snipe.
As an irrelevant aside, I suggest (and I do not have Vasmer's etymological dictionary at hand) that the meaning "fop" or "dandy" linked with the root derives from the "goldfinch" meaning since the bird (unlike the "Spotted Redshanks) is extremely colorful. Note too that the English "popinjay" (fop) is a "folk etymology" coming from the same source as the Russian "popugai" (parrot).