The teacher's plan (according to #2 son) was to fill the whole mug with brown-stained glue. That sounded wasteful, so I decided to provide the bulk of the "hot chocolate" with scrap.
- Mug - any old mug will do, preferably plastic in case of accidents.
- An old drink-can.
- Something sharp to cut the can.
- Some polystyrene packing (from under a frozen pizza).
- PVA glue.
- Cocoa powder.
- Something to stir the glue.
- Hot-glue gun.
You will also need materials to clean up - warm water, tissue and cotton-buds proved perfect.