Prepare a cookie sheet with parchment paper and set to the side.
Mix the flour, cornstarch, baking soda, and salt in a small bowl. Set to the side.
Using a hand mixer or a stand mixer with a paddle attachment, cream the butter and cream cheese with the granulated and brown sugar until light and fluffy, about 2-3 minutes. Scrape down the sides of the bowl as needed.
Add in the egg, followed by the vanilla, and continue to mix.
Gradually add in the dry ingreidents, scraping down the sides of the bowl as needed.
Mix the Oreos, white chocolate chips, and semi-sweet chocolate chips on low or with a rubber spatula.
Form the cookie dough into balls using a cookie dough scoop and place on a dish or the prepared cookie sheet. Chill the dough in the refrigerator for 1 hour.
As the hour is up, preheat the oven to 350. Then, bake the cookies in the oven for 12-15 minutes, until the edges of the cookies are firm.
Let the cookies slightly cool on the cookie sheet before moving them to continue to cool on a cooling rack.
