SO...taking inspiration from Pinterest, and with advice from Sara and Keeley - who've tackled this cake for their own kiddos, I made what looked like just a nothing-fancy vanilla cake.
Oliver and OB had to help finish it, by putting colored sprinkles on the top...(the final ingredients for this science experiment)....
THEN...I cut a slice- revealing that the sprinkles turned the cake RAINBOW inside!!
So fun to see their amazed faces and squealing excitement!
I'd say it was a hit.
Now I need to start planning next year's cake...