Risk management could be addressed something like this:
Establish the aircraft in the appropriate configuration at 2,000 feet.
Reduce power on both engines and maintain altitude until stall is imminent and note speed and recover.
Fail the critical engine for the Vmca demonstration.
If Vmca is not achieved at ten knots above the stall, leave foot under the active rudder pedal and immediately simulate Vmca.
If Vmca is achieved at or better than ten knots above the stall then the exercise has been successful.
In either event recover closing both throttles and lowering the nose.
Clean-up, climb out and continue with the rest of the training.