Engineering students encounter many threshold concepts as they learn the design process. These troublesome yet transformative concepts can hinder learners as they transition from novice to informed designers. A parallel and dueling effect can occur as engineering design educators learn to surmount their own threshold concepts in their journey toward proficient and expert teaching. Until educators develop Design Pedagogical Content Knowledge (DPCK), their students may continue to struggle as they work to overcome the troublesome elements of design. This paper proposes a framework to support the professional learning of engineering educators as they develop D-PCK. Acquiring this competency helps facilitate a shift from dueling to ’dualing’ threshold concepts where educators who make the effort to overcome their own teaching-related threshold concepts become better equipped to support learners as they become better informed designers.