BPMN 2.0 Spec, p. 304:
"By default, compensation is triggered synchronously, that is the compensation throw event waits for the completion of the triggered compensation handler. Alternatively, compensation can be triggered without waiting for its completion, by setting the throw compensation event's waitForCompletion attribute to false."
See the IntermediateThrowEventHandler, to start with.
Implement using a signal-created timer job, of course.