Prepare a large baking sheet with parchment paper and set aside.
In a large bowl, combine the cake mix, vegetable oil, eggs and vanilla. Stir until well mixed. Set the bowl in the refrigerator for 20 minutes to chill.
About 5 minutes before you pull the dough out of the refrigerator, set the oven temperature to 350°F.
Roll the dough into balls and place on the baking sheet.
Bake for 8 to 10 minutes, just until the edges have sent. Do not overbake.
Remove the cookies from the oven and let them cool on the baking sheet for a couple of minutes before transferring to a cooling rack to cool completely.
Meanwhile, melt the chocolate in a bowl over a double boiler pot until it is smooth and completely melted. Remove the chocolate bowl from the double boiler pot and set it aside. If using melted wafers, you can melt them in the microwave at 30-second intervals, stirring between each, until smooth.
Dip half of the cookie into the melted chocolate and cover it in sprinkles. Once the cookies have all been dipped in the chocolate and covered in sprinkles, let them sit for 10 minutes or place them back into the refrigerator for 5 to 8 minutes so that the chocolate can harden.