I guess, it's a bit of a stereotypic name for chocolate based old-fashioned desserts.There was a popular cake in the USSR called "Negro in foam/suds" ("Негр в пене"). It still goes by that name even if commercially produced. They'll probably change it eventually too.
Here's the picture:
For those who don't know any Russian, I'd like to stress the fact that the word "негр" ("negro") in Russian language was (and still is, to some extent) absolutely non-judgmental and neutral. It was an official and acceptable term for a person of African decent, and only for a decade or so it have been actively eliminated from usage, since it's considered offensive on the other side of the globe. The irony is that it was never used as an insult until people were repeatedly told that it can be used like that.