PCK (Pedagogical Content Knowledge) is that special mixture of deep content knowledge and deep pedagogical knowledge which results in specialized knowledge around a subject that grows with the years of teaching experience. We present our approach to foster development of PCK during university based teacher education; namely by including our teacher students in cyclic processes of researching and developing teaching models. In this paper, we describe our approach for fostering PCK through reflection on the activities of planning and teaching, and how we included this in our cyclic model. We also present first results from an evaluation of students' PCK. Based on the empirical data we present a preliminary model of development steps of PCK, describing three competence levels divided in the dimensions 'teaching', 'learning', and 'other'.