Preheat the oven to 400°F. Whisk together the All-purpose flour, cake flour, baking soda, baking powder, cinnamon, cornstarch and salt together in a large bowl. Set aside.
Place the cold, cubed butter into the bowl of a stand mixer and secure the paddle attachement. Turn the mixer on the lowest setting. I keep mine on “stir” the whole time.
Let the mixer cream the butter for 30 seconds, and then add in the brown sugar and mix 30 seconds, followed by the white sugar for 30 seconds or until light and fluffy.
Then add in the egg, egg yolk and vanilla extract and blend until mixed. If any of the butter gets stuck on the paddle attachment use a rubber spatula to knock it off.
Keep the mixer on low speed, gradually add in the flour mixture. I add in about 1/4 cup at a time. Slowly and carefully add it in a little at a time until ingredients are incorporated.
Then add in the white chocolate chips and mix just until the chocolate chips are incorporated. Turn off the machine.
Measure out ~6, 5.5 oz. cookies. I like to use a food scale for this but if you don’t have one, simply eye-ball it. Cookies will be a little smaller than a fist, huge I know! Keep the cookies nice and tall and don’t flatten them. Roll the dough in the cinnamon sugar mixture. Place cookies on a cookie sheet. You can use a silicone baking mat or parchment paper if you prefer.
Bake cookies for 10-11 minutes (see recipe notes if cookies are gooey). The secret is to pull them out before you think they are done. Let them rest on the cookie sheet for 15 minutes and then transfer them to a cooling rack. It’s hard to wait. Trust me, I’ve been there. Let the cookies cool on the cooling rack to finish cooling completely. Cameron likes to enjoy them 15 minutes out of the oven, and I like them best ~45 min-1 hour later. Enjoy with a big tall glass of milk!