No need to wash out the high speed blender - add the cashews, dates, beetroot, water and vanilla, and blend until smooth.
Pour this filling onto the base, but reserve approximately ½ cup.
To the reserved amount, add the cacao and molasses and stir to combine.
Carefully fold through this chocolatey filling into the pink beetroot filling - do not overmix, just swirl through the batter a few times to create a marbled effect.
Top the cake with the balls made from the reserved base.
Freeze the cake for 3 hours (or longer if desired).
To serve, run a sharp knife until hot water before slicing.