In this paper we suggest a new approach for authoring tangible augmented reality applications, called 'immersive authoring.' The approach allows the user to carry out the authoring tasks within the AR application being built, so that the development and testing of the application can be done concurrently throughout the development process. We describe the functionalities and the interaction design for the proposed authoring system that are specifically targeted for intuitive specification of scenes and various object behaviors. Several cases of applications developed using the authoring system are presented. A small pilot user study was conducted to compare the proposed method to a non-immersive approach, and the results have shown that the users generally found it easier and faster to carry out authoring tasks in the immersive environment.