How much torque is needed to mix melted marshmallow with rice krispie?

I am designing a robot to make rice krispie treats!

More specifically, I want to use a fork to mix the melted marshmallow with rice krispie. I am currently specing out the motor, and since marshmallow+rice krispie is not a typical engineering material, I am struggling to find out theoretical viscous force for my mixture, which I think is the main force that my motor needs to overcome. Alternatively, I want to create this scenario in lab and find out experimentally how much torque I need to apply and for how long in order to thoroughly mix the two. One idea I have is to set up a jig that mounts a high torque stepper motor to the fork, spin it about its tall axis, and gradually increase current to observe mixing results. But this method will take some time to set up.

Do you know a quicker and more accurate way I can figure out how much torque I need to apply in order to mix these two experimentally? Or do you know a way to figure this out theoretically without needing to build anything? Welcoming creative solutions!