This article addresses one way in which decades of mathematics education research results can inform practice, by offering a framework for designing and implementing an in-service teacher education programme for upper secondary mathematics teachers in Denmark. The programme aims to educate a "task force" of so-called "maths counsellors", i.e., mathematics teachers whose goal it is to help identify students with genuine learning difficulties in mathematics, investigate the nature of these difficulties, and carry out research-based interventions to assist the students in overcoming them. We present and discuss the various components of the programme, theoretical as well as practical, and account for how these make up a framework for designing a research-based "maths counsellor" teacher programme.