This is definitely not my original idea, but I didn't have a particular "recipe" that I followed, so we kind of put our own twist on it.
All you need is a little bit of milk, some food coloring and some cheap foam brushes (Michael's has them on sale this week for 25 for ONE dollar!...Yes, we stocked up).
You also need your canvas of choice. Today, ours was marshmallows. I've seen people do it with bread (and then toast it!) or popcorn even. Then you just let them create!
The finished product...