From 2016 to 2020, a team of K-12 and higher education mathematics educators worked to address the need for high-quality online learning by creating a multisession, fully online professional learning course. As the team worked to design and facilitate online professional learning, the goal was to maintain the core aspects and guiding principles of high-quality in-person professional learning, as articulated in research and in the Standards for Professional Learning (Learning Forward, 2011). In particular, the team worked to design online professional learning that established collaborative learning communities and was grounded in research and models of human learning -- common practices of in-person learning that are challenging to maintain online. Through this project, the team learned valuable lessons about how to make the technology work in service of the learning. This article aims to serve as an illustration of how to maintain high-quality professional learning in an online space.