Preheat your oven to 350 degrees Fahrenheit (175°C) and line two baking sheets with parchment paper.

In a bowl, whisk together the all-purpose flour, cornstarch, baking soda, and salt. Set this dry mixture aside.

In a stand mixer fitted with the paddle attachment, cream together the softened butter and granulated sugar until the mixture is light and fluffy.

To the creamed mixture, add the large egg, lemon zest, lemon juice, and vanilla extract. Begin by adding only ½ cup of the flour mixture to prevent curdling. Mix until everything is well blended.

Gradually mix in the remaining flour mixture in two additions, using a low speed setting until the flour is just incorporated into the dough.

Gently stir in the mini white chocolate chips until they are evenly distributed in the cookie dough.

Portion Dough: Using a ¼-cup scoop, portion out the cookie dough and drop it onto the prepared baking sheets. To ensure consistent cookie sizes, aim for around 55 grams per cookie. Place the cookies well apart on the sheets, with no more than 4 cookies per tray.

Bake the cookies at 350°F for 10 to 12 minutes or until the edges of the cookies start to turn golden. Be cautious not to overbake them.

Allow the cookies to cool on the baking sheets for 5 minutes before carefully transferring them to a wire rack. Once they are completely cooled, dust the cookies with powdered sugar for a delightful finishing touch.