Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
Cream together butter and sugar until light and fluffy.
Beat in eggs and vanilla extract until fully combined.
In a separate bowl whisk flour, cornstarch, baking powder, baking soda, and salt.
Gradually mix dry ingredients into wet ingredients until combined.
Fold in confetti sprinkles and white chocolate chips if using.
Scoop large dough balls and place on prepared baking sheet, slightly flattening the tops.
Bake for 10–12 minutes until edges are lightly golden but centers remain soft.
Cool on baking sheet for 10 minutes before transferring to a wire rack.