I'm afraid that "krojesz" is not a word...
"kroisz" is 2nd person singular, but that's just a Present Tense declarative form, so it's "You are cutting meat".
"krój" is technically the imperative 2nd person form, but as it's imperfective, that doesn't make much sense in this example.
"pokrój" (perfective, ergo: cut it 'succesfully' and finish it) is the right form in your sentence :)
Well... I'd say that "kroić" is simply "to cut in a way that makes most sense in the given situation".