A metaphorical term to describe a lesbian. Imagery of the famouscornish pasty is used to replicate the act of scissoring in which a females pasty-like vagina is 'smashed' against another's. Hence Pasty smashing.
When you feed a woman only collard greens (like a lot of collard greens) and then fuck her ass on St. Patrick’s day. This results in a wonderfully odorous layer of green shit on your cock, fit for any Irish celebration.
Matt: Yooo dude, my dick still smells from that Saint Patty’s day treat.