What is Cooking Up?
1.
preparing for a shot of heroin
Sick Boy: Say something Mark.
{shouting}
Sick Boy: Fucking say something, huh?
Mark "Rent-boy" Renton: I'm cooking up.
- Trainspotting (film)
See
2.
To make deal with sb,usually underground or illegal.
what do you got cooking up with him?
See