I'd not go with a VSD on any sort of an agitator/beater drive motor and especially with something that has the viscosity of ice-cream.
Reason I say that, is because you need to be able to get this product moving for a start, this is where you need the initial "oomph" from a DOL starter, to get the drive unit turning in the first place.
This is only my thoughts on this, I could be way wrong too, I've worked with milk vat agitators in 22,000L refrigerated vats before and getting the blades of the agitator to turn first off with a VSD on it, was just about impossible.
What you need to think about is the amount of force required to get that beater turning.
Hope that this of some help.
Let's face it, these days if you're not young, you're old - Red Green