I originally saw this idea here and she called it Bubble Dough, so I'm going with it.
We have been experimenting with cornstarch a lot lately, it's cheap, generally is easy cleanup, and it makes really fun sensory materials.
I explained to A what we were doing and then let him run with it.
He was unsure at first but got into it and our bubble dough started to take shape.
I didn't pay attention to the recipe included in the original post (I didn't think there was one, but I just went to check, and there is. Oops!) So I got a little over zealous with the cornstarch and we started with an entire box. This worked out ok for us since we buy our liquid dish soap at Costco, for the rest of you, you might want to start out with around a cup of cornstarch.
A mixed and mixed, and apparently we took a photo break somewhere in there, because eventually we ended up with this...
It's kind of a cross between Playdough and Gak (does anyone even remember Gak!?) It has a thick enough consistency that you can shape it and use cookie cutters on it, but if it sits for a couple of minutes it starts to spread and settle. We ended up with about a quart of this stuff and I'm keeping it in a Zip-lock bag in the fridge, where it seems to be happy in between play times.