Episerver Block Controller error

I am expanding my horizons in the CMS world to add Episerver to the list of platforms I develop on, and the process is a bit of trial-and-error, with an emphasis on the "error" part the past couple weeks. I am coming into this without attending any Episerver training, so this may be known to everyone else, but, nevertheless, I found this error rather intriguing and wanted to share in case someone else missed the cause due to lack of coffee.

I am building a site using MVC, and with that comes the creation of a block class, and a block controller. I added my block to my Page model and then proceeded to create the controller. Using the standard approach in Episerver, I named the controller and block to match, with the block called CalloutBlock, and the matching controller CalloutBlockController. After copying some code into my controller, building, and refreshing my page, I was greeted with the following, lovely message: