Preheat oven to 350°F. Line a baking sheet with parchment paper. Set aside.
Whisk together all purpose flour, cornstarch, baking soda and salt in a medium bowl. Set aside.
In a large mixing bowl or bowl or a stand mixer, cream the butter and brown sugar together on medium speed until light and fluffy, scraping down the bottom and sides of the bowl as needed, about 2 to 3 minutes.
Add the vanilla extract and the egg and beat in until combined, about 1 to 2 minutes.
Add the dry ingredients in two parts, mixing just until combined, scraping down the sides and bottom of the bowl as needed. Do not over mix.
Fold in the white chocolate chips until evenly distributed and then gently fold in the blueberries.
Scoop about 2 tablespoons of cookie dough, gently roll into a ball and place on the prepared baking sheet about 2 inches apart.
Bake for 9 to 10 minutes or just until golden on the edges. Do not to over bake.
Allow the cookies to rest on the baking sheet for 5 to 10 minutes before transferring them to a wire cooling rack to cool completely. Enjoy!