How to Make It
Beat butter and sugar in a large bowl with an electric mixer until combined. Add flour, cake mix, salt and vanilla, mixing until combined. Add milk, 1 tablespoon at a time until a dough consistency is formed.
Roll dough into 1-inch balls and place on parchment or wax paper on a baking sheet. Chill truffle dough for at least 15 minutes or until firm.
Melt white candy melts according to package directions. Using a fork or dipping tool dip truffle balls into melted candy, rolling to coat. Place on wax paper to dry (about 15 minutes).
Melt blue candy melts according to package directions and place in a ziptop bag or small piping bag. Cut the tip off the bag. Drizzle blue candy melts over the truffles. Sprinkle the tops with a small amount of red nonpareils, if desired. Chill truffles until ready to serve.