Teaching parallel programming and HPC is a difficult task. There is a large number of sophisticated hardware and software components, each complex on their own and often showing non-intuitive interaction when used in combination. We consider education in HPC among the more difficult topics in computer science due to the fact that larger distributed memory systems are ubiquitous yet inaccessible and intangible to students. In this work, we present the Cluster Coffer, a miniature cluster computer based on 16 ARM compute boards that we believe is suitable for reducing the entry barrier to HPC in teaching and public outreach. We discuss our design goals for providing a portable, inexpensive system that is easy to maintain and repair. We outline the implementation path we took in terms of hardware and software, in order to provide others with the information required to reproduce and extend our work. Finally, we present two use cases for which the Cluster Coffer has been used multiple times, and will continue to be used in the upcoming years.