The only thing I can think of is “are you slammed?” When a lot of customers arrive at once and the cook is super busy filling their orders, he is said to be “slammed”. If the cook answers “yes”, that would suggest that he has no time to make breakfast for his coworker at the moment. In your question, you don’t specify who said “you got me”, so I cannot give an exact interpretation, but it would normally mean “you’ve understood”. When you write “Later he made what he wanted”, it’s clear that the second “he” is your coworker, but does the first “he” refer to your coworker or to the chef? Who made breakfast for your coworker? How much later? In the future, please try to include all relevant information so that we can answer your questions better.

This is not a phrase. The only thing that makes sense is that he is referring to a Grand Slam breakfast or you may have misheard. I'm not sure.