flat whoopie pies :(

Ok any cooks out there. I find a whoopie pie recipe it says to use regular cake mix and put spoonfuls on a cookie sheet cook for 10 minutes. So I did and they came out as thin as my crepes what did I do wrong. I wanted big fat whoopie pies and I could not figure out how to get them that way. So besides making them completely from scratch does anyone know what to do different.
I make my cookies from scratch but was looking for a quick snack. They were still edible, Ray and Michael didnt seem to care they tasted ok but just not what I was looking for.