Preheat the oven to 350 degrees Fahrenheit and line baking sheets with nonstick baking mats or lightly spray them with nonstick cooking spray.

In the bowl of an electric mixer, cream together white cake mix, melted butter, vanilla and egg. Stir in jimmies by hand.

Scoop or roll dough into rounded 1 1/2" balls and place at least 2" apart on prepared sheets. Press dough balls down with the palm of your hand to flatten the balls slightly. Bake for 8-9 minutes.

Allow them to cool slightly on the baking sheets before removing them to a cooling rack to cool completely.