If you pile enough old fashioned toffee together you can exceed it's critical mass, and it starts it's own chain reaction, glowing white hot and emitting Alfa Particles*
This is another exercise in lighting. The more I try, the more I learn: Here I am using remote flash to light a subject from underneath. Combine this with a suitably short shutter speed to get this glowing coals effect.
*As any owner of Italian cars will know, Alfa Particles cause painted steel to rust spontaneously from underneath. By the time the paint bubbles, the steel has already gone. This also explains why old fashioned toffee is suspiciously rust coloured.