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Hi, Everybody,

I do not get get the meaning of this phrase "Someone notched below the black belt in tiramisu." Any ideas? Thanks in advance!

Here is some context:
We got some crazy martial arts in this movie
that you might know, some tiramisu. It's Australian fighting style. Someone notched below the black belt
in tiramisu.

-Tiramisu?
-Oh, yeah, baby.

-That's an Italian dessert, you asshole.
-Oh, really?