Start by placing the cubed cold butter and granulated sugar into the bowl of a stand mixer. Beat them together using the paddle attachment until the mixture becomes light and fluffy. Gradually increasing the mixing speed helps properly incorporate air into the dough. This step helps create the thick bakery-style texture.
Crack the eggs into the bowl one at a time while mixing. After each addition, mix until fully combined so the dough stays smooth. Then add the vanilla extract and continue mixing briefly until everything is evenly blended.
Add cornstarch, baking soda, salt, cake flour, and all-purpose flour to the bowl. Mix slowly until the ingredients combine and form a thick cookie dough. The combination of cake flour and regular flour helps create a tender yet sturdy cookie.
Gently stir in the chopped circus animal cookies, white chocolate chips, and rainbow sprinkles. Mix until the ingredients are evenly distributed throughout the dough. These mix-ins add flavor and help maintain the structure of the cookies during baking.
Place the cookie dough in the refrigerator and let it chill for about 20 minutes. This step helps the dough firm up and prevents excessive spreading when baking. Chilling also allows the flavors to develop more deeply.
Preheat the oven to 400°F and line a baking sheet with parchment paper. Measure about 6 ounces of dough for each cookie and form it into a loosely shaped ball. The rough shape gives the cookie its classic craggy bakery-style look.
Place four dough balls on the baking sheet, spacing them about three inches apart. Bake one tray at a time in the center of the oven for about 10–13 minutes. The outside should look lightly golden while the center remains soft and slightly underbaked.
Remove the cookies from the oven and allow them to cool on the baking sheet for about 30 minutes. They will continue cooking slightly as they cool. This resting time also helps them firm up without losing their gooey center.