"Dutch" in this case probably refers to a method of processing chocolate; recipes using chocolate are often called "double Dutch" to emphasize their chocolate deliciousness :)

"Double Dutch" is also a children's jumprope game; the rhythm of these lyrics is reminiscent of the rhythm of some of the chants used in jumprope. According to Wikipedia, Double Dutch "became an element of hip-hop culture," so it's possible that the term here refers to both the game and the chocolate.

"Kisses" may be a play on the usual kind and also a well-known chocolate candy produced by Hershey called "kisses."

"Back to Africa" may possibly refer to a historical movement in the 19th century US to send American blacks, both free and slave, back to Africa. Considering the rest of the song, probably not; but it's interesting to read about: http://en.wikipedia.org/wiki/Back-to-Africa_movement

I hope the vat at the wacky factory is self-explanatory.

"Double Dutch darky" could mean "pure darky," I suppose, but I think it's more likely to mean "chocolate darky." Say someone's girlfriend got a dark tan. He might say, "Wow, you're the color of cinnamon. Give me a kiss, you little cinnamon bun."  That's how I see this, as almost affectionate.

These lyrics were taken from a poem by a black poet named Harryette Mullen, which puts a different slant on the  idea that it is a racist assertion. The nearby verses (also heavy with wordplay) talk about skin creams. The poet seems to be criticizing the fact that skin care companies sell creams intended to lighten the skin of black women.

http://www.afropoets.net/harryettemullen4.html