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

In a stand mixer, combine unsalted butter, brown sugar, and granulated sugar. Beat until light and fluffy.

Add in the egg and vanilla extract, mixing until combined.

In a separate bowl, whisk together flour, cornstarch, baking soda, baking powder, salt, and cinnamon. Gradually add to the wet ingredients.

Fold in chopped pistachios and white chocolate, reserving some for topping.

Scoop dough into balls and place on prepared baking sheets, spacing them apart. Top with reserved nuts and chocolate.

Bake for 10-12 minutes until edges are golden brown, then cool on baking sheets for 10 minutes.

Transfer to a wire rack to cool completely.