Smash Ya Pasty is a slang word of North East England origin which means a man will have sex with a women very well,so much that the women will feel like there vagina has been literally smashed.
Used as a response to point out an unintentional double-entendre in which the original speaker could be taken as intending to perform some act that would be more appropriate for a sex, kink, or other "special" party.
Last night I got lucky with this rough bird, went back to her place, and I got the hell outta there this morning before she got her smashed pasty our for seconds!