These biscuits are called Hobnobs over here.
And in the words of the great Peter Kay on the subject of biscuit dunking:
"Hobnobs are like marines, hobnobs. They're like the bloody S.A.S. of the
biscuit world, hobnobs. You dip a hobnob, it's like, 'Again! Again! Dip
me again, I'm going nowhere me, son, dip me! Is that all you've got?