Preheat oven to 350°F. Prepare three baking sheets by lining them with parchment paper.
In the bowl of a stand mixer with a paddle attachment (you can also use a hand-held mixer) add butter, cream cheese, brown sugar, and confectioners' sugar. Beat on high for 2-3 minutes or until ingredients are fully combined. Scrape down the sides of the bowl as needed.
With the mixer on its lowest speed, add in the egg and vanilla and blend for about 1 minute.
Add in the flour, cornstarch, baking soda, and salt. Then, turn the mixer on low and mix for about 1 minute, or until ingredients are fully incorporated.
Fold in the white chocolate chips, mixing by hand.
Finally, fold in the diced strawberries, reserving ¼ cup for the topping.
Using a 3-tablespoon cookie scoop, scoop batter out onto cookie sheet. I fit 8 cookies on two sheets then 4 cookies on the final prepared cookie sheet. (20 total cookies)
Add the reserved diced strawberries to the tops of the cookies. Using your hand or the bottom of a kitchen glass, press the cookie dough down so that it is not rounded on top and the added strawberries are pushed into the dough.
Bake for 8-10 minutes. Cookies are better when slightly underdone and just barely brown on the edges. Keep a close eye that they do not get dark brown.
Allow cookies to cool for 5-10 minutes before moving to cooling rack.