This phrase is used when sayin something you did or should have did in the past.
James: yo who that?
Kai: thatâs jada, I use to talk to her Back in da cheese at my old school.
Back in da cheese is a phrase/reference to back in the day or a minute ago
James:yo who that?
Kai: thatâs jada I use to talk to he (Back in da cheese)