Green’s Dictionary of Slang

blow the froth off! excl.

[blow the froth (off) v.; the idea is of removing the superfluous]

(Aus.) a dismissive excl., stop being silly!

[Aus]L. Esson Woman Tamer in Ballades of Old Bohemia (1980) 71: chopsey: I’d get lots o’ things for you, Katie: [...] I don’t forget how you stuck to me. / katie: Ah, blow the froth off. / chopsey: Straight, I’ve had a bit of luck at last.