Preheat the oven: Preheat the oven to 400°F (204°C). Line a baking sheet with parchment paper or a silicone baking mat.
Whisk dry ingredients: In a medium bowl, whisk together the all-purpose flour, cake flour, cornstarch, cinnamon, cream of tartar (if using), baking powder, baking soda, and salt. Set aside.
1¼ cups all-purpose flour, 3/4 cup cake flour, 1 tsp. cornstarch, 1 tsp. ground cinnamon, 1/2 tsp. baking powder, 1/2 tsp. baking soda, 1/2 tsp. salt, 1 tsp. cream of tartar
Cream butter and sugars together: In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer), beat the cold, cubed butter with both sugars on medium speed for 1-2 minutes; it will sort of look like a paste since butter is cold. Scrape down the sides of the bowl as needed.
1/2 cup unsalted butter, 1/4 cup granulated white sugar, 1/2 cup packed brown sugar
Add eggs and vanilla: Mix in the egg, egg yolk, and vanilla extract until fully incorporated and smooth.
1 large egg, 1 large egg yolk, 1 tsp. vanilla extract
Add dry ingredients: With the mixer on low speed, gradually add the dry ingredients, mixing just until the dough comes together. The dough will be thick.
Add in chocolate chips: Add in the white chocolate chips and mix just until combined.
2 cups white chocolate chips
Form cookie dough balls: For bakery-style cookies, you’ll portion the dough into 6 large balls. Roll each dough ball in the cinnamon-sugar mixture until fully coated. Do not flatten.
1/2 tsp. ground cinnamon, 2 Tbsp. granulated white sugar
Bake: Arrange on the prepared baking sheet, spacing them out well. Bake for 10-11 minutes, or until the edges are set but the centers still look slightly soft and the tops are a little golden.
Cool: Allow the cookies to cool on the baking sheet for 15 minutes before transferring to a wire rack to cool completely. The centers will continue to set as they cool.