Obviously a notorious serial killer with serious mental health problems and delusions isn't the most reliable source, but the other half of his letter (wrote in 1934) about his murder confession was deemed true.
More info on the wikipedia (with sources): https://en.wikipedia.org/wiki/Albert_Fish#Letter_to_the_mother_of_Grace_Budd
This appears to be an unpleasant fantasy.
The American diplomat WW Rockhill, who was working in the American legation in Beijing in 1894, wrote an extensive study of China's population history for the Smithsonian in 1904. This went into considerable detail on the subject of famine in China during his years in the country. Rockhill does mention an extensive dearth in the north-west of the country in 1892-3, the effects of which were still being felt in 1894 – "great drought and famine in Shan-hsi [Shanxi], Shen-hsi [Shaanxi] and Chih-Li [Zhili], and southern Mongolia" – but nothing about famine in Canton; none of these regions is anywhere near Hong Kong.
Hong Kong was, in 1894, a British colony, so I also did a search of newspapers in the British Newspaper Archive for that year. These reveal that there was a significant outbreak of plague in the city in June of that year, which killed about 1,700 people. The outbreak was covered in a number of British newspapers, which confirms that disasters in Hong Kong would be reported in the British press. It is therefore likely conclusive that not a single story about famine in Hong Kong appeared in the tens of thousands of pages of digitised British newspapers in the BNA for 1894.
Sources
British Newspaper Archive for 1894
William Woodville Rockhill, "Inquiry into the population of China", Smithsonian Miscellaneous Collections 2 (1904)
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