They used an Arduino to control the temperature and a motor shield to power the peltier plate. It kind of worked but they discovered it was difficult to assess the physical state of the chocolate.

New Book Release The new book, PID-Based Practical Digital Control with Raspberry Pi and Arduino Uno , is about using the Raspberry Pi 4 and Arduino Uno in PID-based automatic control applications.

This is a replacement for the commercial PID unit he used on the original build. That monitored the temperature in the smoker, using predictive algorithms to maintain just the right heat level.