Using a large bowl, cream together the butter and cream cheese until combined and smooth
Beat in the egg and vanilla until combined
Mix in the cake mix.
Fold in ¾ C of the sprinkles
Cover with plastic wrap and place into the fridge overnight
Preheat the oven to 350 degrees and line two cookie sheets with parchment paper or a silicone mat
Using a small ice cream scooper, scoop out some of the dough and roll it into a ball
Scoop the powdered sugar into a large bowl
Sprinkle the cookie ball with some more sprinkles then roll the ball in the powdered sugar until completely coated
Place onto the cookie sheets
Bake in the oven for 8-10 minutes or until lightly brown
Allow cooling for a few minutes before placing onto a wire rack to cool completely
Using a heat-safe bowl, melt the white chocolate in 30-second increments in the microwave until completely melted
Carefully Dip half of the cookie into the white chocolate
Very gently shake any excess white chocolate off
Place the cookie onto the parchment paper or silicone mat
Sprinkle some more Christmas sprinkles
Allow the chocolate to completely harden before enjoying it!