In the bowl of a stand mixer, cream together the cubed cold butter and the granulated sugar with the paddle attachment on low speed for 30 seconds. Increase the speed to medium and continue mixing for 30 seconds. Lastly, increase the speed to high and mix for another 30 seconds until butter mixture is fluffy and light.
Beat in the eggs, one at a time, followed by the vanilla, until mixture is combined. Lastly, add in the cornstarch, baking soda, salt, cake flour, and all-purpose flour, mixing until incorporated. Lastly, stir in the chopped frosted circus animal cookies, white chocolate chips and the sprinkles until fully combined. Refrigerate the dough to chill for 20 minutes.
Preheat your oven to 400° degrees F. Line 1 baking sheet with parchment paper. Using a digital cooking scale, weigh out 6 ounces of dough and form it into a loosely packed, rough textured ball - I like to form my cookie dough balls kind of on the taller side. Place staggered 3" apart, 4 dough balls per sheet, on the baking sheet.
Bake in the center rack of the oven, one sheet at a time, for 10-13 minutes or until light golden brown and the exterior looks dull and dry. The centers should be gooey and underbaked. You can always test bake one cookie first to gauge what your best timing is. Remember, the cookies will continue to finish cooking as they cool on the baking sheet, so do not over-bake. Remove from the oven and let cool on the baking sheets for up to 30 minutes as cookies are quite fragile after being baked. Keep remaining dough refrigerated while other cookies are in the oven.