While his ideas for cooking magic tools would work, the most simple way of using magic tools for cooking would actually just be pulsing it. All you'd need is a basic heating tool and a cooktop or cookware that retains heat, instead of needing a bunch of tools tuned to different temperatures or a mechanism to control the height of the tool. It's the same principle used in electric stoves, but I'd assume they can't achieve full PWM so it'd be reliant on the heat retention instead of being able to just pulse it thousands of times per second.