Preheat the oven to 350 degrees F. Line two baking sheets with parchment paper. Set aside.
In a medium bowl, whisk together the flour, cornstarch, salt, baking soda, and baking powder. Set aside.
In the bowl of a stand mixer, cream the butter and sugars together until light and fluffy. Add the egg and vanilla extract and beat for another minute or so.
Add the flour mixture and beat until just combined. Next, add the oats and white chocolate chips, beating until things are just combined.
Using a spatula, gently fold the blueberries into the cookie dough, being very careful to not break them.
Use a small cookie scoop to scoop the dough onto the prepared cookie sheets. Leave about 2 inches between each ball of dough.
Bake for 19 minutes, or until the cookies are golden brown. Allow them to cool on the pan for about 5 minutes before removing them to a wire rack to finish cooling completely.