As an Japanophile, it would be a crime for me to have not known. In fact, I think I may have even had my manga rights revoked.
When I first heard the song, I knew panko was some kind of Japanese deep fried dish but that's all I knew (and all I still know).
Shrimp tempura and panko fried ice cream. If you've never tried Japanese food before, start there. I was born in Japan (my parents are not Japanese though), so I guess I had a taste for Japanese food for a long time. It's not really a dish, it's an ingredient. It's basically like bread crumbs for frying but tastes way better.
I had to use Google to find out what panko was. Despite being a clever reference to Mike's heritage, the word still seems a little out-of-place in the context of what the song is about. Then again, KTTK may be open to multiple interpretations, as most LP songs are.
What does it mean? It means Mike is half fried-bread. Which means someone now has to Photoshop Mikes head onto a slice of fried-bread.