Don’t pepper my jelly

Slang way of (playfully or seriously) saying “if you keep it up you’re gonna make me upset”
I.E. Don’t test my limits
Don’t piss me off
Don’t add fuel to the fire

A friend is being rude about you having a good time and they keep trying to bring down your vibe by making you angry

“Don’t salt my jam and don’t pepper my jelly”
(Don’t burst my bubble and don't test me”)

“Quit peppering my jelly”
(You’re pissing me off)