MSI at the University of Minnesota has adopted a goal of supporting Interactive HPC as a first class service. This paper describes the implementation of a gateway for user-friendly, reproducible computing in an HPC environment using the Jupyter notebook server and Jupyterhub. For this project, we developed novel components and techniques enabling interoperability of Jupyter with the distinct requirements of an institutional HPC center. These include modules providing integration with batch job scheduling, control of job profiles, and integration with a central authentication service. To achieve software sustainability, we designed these elements for generic applicability, and several have now been accepted as components of the Jupyterhub open source project.