In a medium bowl, combine flour, cake mix and baking soda, then set aside.
Cream together softened butter and sugars until smooth. Add the egg and vanilla and mix together.
Add the flour mixture until just combined. Then fold in chocolate chips and sprinkles, if using,
Scoop dough into balls and refrigerate for 1 (or more) hours, up to 3-4 days (covered). Press tops of balls into extra sprinkles right before baking.
Bake for 10-12 minutes. Remove cookies from oven when edges are slightly browned (centers may still be soft). If desired, press more chocolate chips onto the cookie tops. Let cool.