In a mixer fitted with a paddle attachment, cream butter and sugar until light and fluffy.
Add egg and vanilla extract. Mix until combined.
In a medium bowl, whisk together flour, pudding mix, salt, baking powder, baking soda, and cream of tartar.
Add to mixer on a slow speed. Mix until just combined.
Stir in white chocolate chips, chocolate chips and sprinkles.
Using a medium scooper, scoop out dough balls and put them in the fridge for at least an hour.
Preheat the oven to 350 degrees and prepare a baking sheet with parchment paper.
Place the cookie dough balls on the baking sheet and bake for 13-15 minutes.
Allow cookies to cool on baking sheet. Once cooled, place the cookies in the fridge for one hour.
Melt chocolate according to package instructions.
Once chocolate is melted, take cookies out of the fridge. Dip each cookie halfway into the melted chocolate.
Place on parchment paper and add extra sprinkles.