In this paper we present the initial conceptual design of an authoring tool for the emergent narrative agent architecture FAtiMA that powers the virtual bullying drama FearNot!. We explain that the process of authoring emergent narrative to a large part consists of designing a planning domain for a virtual character planner and explain the difficulties this task poses to the non-technical author. After reviewing existing authoring tools and evaluating them in terms of their applicability to FAtiMA, we introduce a novel concept of approaching the authoring task, in which the author is playing through example story lines that are used to gradually increase the knowledge and intelligence of a virtual character. This concept is extended by a mixed initiative feature, which allows the author to cooperate with the character planners while providing the example stories. Finally we concretize our idea and explain our intended implementation of it within the FearNot! Framework. We believe that our design, although being specified with a particular architecture (FAtiMA) in mind, may provide some interesting ideas to others, who are trying to solve the authoring problem for interactive storytelling systems.