I've always interpreted it as "thrown into shell" (as in "Eierschale" = egg shell, or even "Bananenschale" = banana peel) rather than "thrown into bowl". (I wonder whether "shell" and "Schale" are cognates?)

Looking at LEO, it may be significant that "Schale" is also glossed as "jacket [tech.]" - i.e., something that covers something else.