Here is my imaginary black tahini recipe: (the amounts given are pure fiction)
1 c. roasted black sesame seeds
1/2 c. oil, take your pick on variety. probably not olive.
Roast the sesame seeds in the oven. I did mine a bit hot, starting at 450 for a few minutes, and then quickly recanting on the whole idea of fire and damnation and settling them down to about 300 after 2 to 3 minutes. They were probably in the oven for about 10 minutes total. It's hard to tell since they're black to begin with, but I pulled them out they were starting to crackle up and a few had discolored to an ashen grey. Try not to worry about them burning.
After the seeds are roasted, toss them into a food processor with a the oil, mix it up a bit to make sure the oil coats all of the seeds, and the process the hell out of them. They should make a delicious heavy black paste.