In a large bowl, combine the yellow cake mix, melted butter, and egg. Mix it up until a dough forms. Itâs going to be a bit thick, but thatâs okayâthatâs the consistency we want for the base. Once itâs all mixed together, press about two-thirds of the dough into the bottom of your prepared baking pan. You want a nice, even layer, so donât rush this part. Itâs the foundation for all the deliciousness thatâs about to come!