The last minute Birthday Hit!
Prepare the boxed cake mix as directed
Now add the rest of the cake batter & put back in oven for the rest of the baking time indicated on the box (test the top portion of the cake with a toothpick)
While still warm(ish) add the topping
I hope you get as many compliments as I have as well as preparing an "instant fav" for everyone!
(It goes really fast)