To be toasted, nicely toasted. In other words, just the right amount of high.
It is a reference to an episode of The Simpsons (S07E24, Homerpalooza), where a member of the band Cypres Hill, in response to a question about what the concert is about, says "That, and getting toasted, nicely toasted."
Breville is an appliance brand in Australia that makes sandwich toasters. A breville is slang in Australia for a toasted sandwich.
"Dude, how are you feeling?"
"Man, I'm brevilled right now, this night is going great!"