So here's the problem.
For simplicity in visualizing the problem, imagine that you have a static mesh shaped like a box. You have a player controlled sphere resting on top of that box. Using torque you roll the sphere off the box. As the ball reaches the "point of no return" where it is going to fall off; apply a strong torque back towards the platform. The sphere will be catapulted forward.
This is easiest to reproduce in one of two ways; get the ball moving at a pretty good speed on a low friction surface, so you can get the ball spinning in the opposite direction, and still keep it moving towards the edge/cliff. An alternative is to have it so that one key torques the ball forward, and another key torques the ball in reverse with 10x-20x the force. Get the ball moving towards the edge, and just before it goes off, hit the high-power reverse, and "spin out".
Any advice would be appreciated.