Sift flour, baking powder and salt into a bowl and set aside.
Cream together butter and sugar for 5 mins.
Add in your egg and vanilla and mix again.
Slowly add in your flour mixture and mix just until almost combined,
Finally gently fold in your sprinkles and white chocolate (if using).
Wrap dough in plastic wrap and chill for about 20-30 mins.
While dough is in fridge preheat your oven to 350°f
Remove dough from fridge and with a cookie scoop or spoon scoop dough onto cookie sheet about 2 inches apart from each other ( I like bigger cookies so I use a med size cookie scoop).
Bake for 10-12 mins, remove and let rest on sheet for 2 mins before transferring to cooling rack.