We present a Problem-Based Learning (PBL) approach to teaching formal methods, using Event- B and the Rodin development environment. This approach has arisen out of a gradual adoption, over a period of 3 years, of Rodin as the main teaching tool. Just as the concept of refinement is fundamental to what we are trying to teach, we demonstrate that it is also fundamental to the teaching process. Through analysis of a small number of PBL case-studies we argue that the changes to our teaching, supported by Rodin, have started to have a positive impact on our students meeting the specified learning objectives (course requirements). However, we also argue that much more work needs to be done in order to improve our teaching of formal methods. Inspired by the analogy between software design and sculpture, we conclude by proposing that formality holds the key to mastering the harmony between the "holes" and the "lumps" in our models