This is stinky tofu, you could say it's fermented tofu but I say it's rotten tofu.
I ate it once, in Beijing and I think I can say it was my worst-food-experience ever. Partly because I hadn't seen it coming when I put it in my mouth, partly because I wasn't used to fermented food back then, but mainly because I think it really is disgusting food. :-)
There is a small chance I would appreciate it a little better nowadays, but stinky tofu is not available in the Netherlands, so I can't test that idea.
It also means I can't photograph it myself, so I used this lovely photo made by Gary Soup. So if you want to use this photo, please don't credit me but Gary!
Wikipedia about: Stinky Tofu.
Daar vind je ook het verhaal over mijn eerste/enige ervaring met dit product.