In a medium bowl, whisk together the flour, cornstarch, baking soda, and salt.
In the bowl of a stand mixer fitted with the paddle attachment (you can also use a large bowl and a hand mixer), beat together the softened butter, brown sugar and granulated sugar at medium speed until creamy. Add the egg, egg yolk and vanilla extract and mix until well incorporated.
Reduce the mixer speed to low and slowly mix in the flour mixture. Add the dried cranberries and white chocolate chips and mix on low speed until just combined.
Cover the bowl and chill the dough in the refrigerator for at least 1 ½ hours and up to 24 hours.
When you are ready to bake the cookies, preheat oven to 350° F. Line baking sheets with parchment paper.
Scoop dough by rounded tablespoonfuls and place 2 inches apart on the baking sheet. If desired, press a few more cranberries and white chocolate chips into the tops of the cookies.
Bake for 8-11 minutes, until cookie edges are barely golden brown and centers are almost set. Be careful to not over-bake the cookies, as they will continue to set up as they cool on the baking sheet. Let cookies cool on the pan for a few minutes before removing to a wire rack to cool completely.