Preheat oven to 350F (175C) and line a baking sheet with parchment paper. Set aside.

In a large mixing bowl (or the bowl of a stand mixer fitted with the paddle attachment), combine the butter and sugars using an electric mixer until light and creamy (about 1 minutes on high speed).

Add egg, egg yolk, and vanilla extract and stir until well-combined.

In a separate, medium-sized bowl, whisk together flour, cornstarch, baking soda, and salt until well-combined.

With mixer on low-speed, gradually add dry ingredients to wet, stirring until completely combined.

Fold in white chocolate chips until evenly distributed.

Drop cookies by 1 ½ tablespoon-sized scoops onto prepared baking sheet, spacing cookies at least 2” (5cm) apart.

Bake in center rack of 350F (175C) oven for 10-12 minutes, edges should be beginning to turn light golden brown, centers may appear slightly underdone, this is fine! Allow cookies to cool completely on baking sheet before enjoying – they’ll be fragile when warm. If desired, gently press additional chocolate chips into the surface of the cookies within 1 minute of removing from the oven.