In a large bowl using a handheld mixer or stand mixer fitted with a paddle attachment, beat the butter for 1 minute on medium speed until completely smooth and creamy. Add the brown sugar and granulated sugar and mix on medium high speed until fluffy and light in color. Beat in egg and vanilla on high speed. Scrape down the sides and bottom of the bowl as needed.

In a separate bowl, whisk the flour, cornstarch, baking soda, and salt together. On low speed, slowly mix into the wet ingredients until combined. The dough will be quite thick. Add the white chocolate chips, cranberries, and pistachios, mix on low for about 5-10 seconds until evenly distributed. Cover the dough tightly and chill for at least 2 hours.

Remove dough from the refrigerator and let sit at room temperature for 10 minutes. Preheat oven to 350°F (177°C). Line two baking sheets with parchment paper.

Once chilled, scoop and roll about 1 tablespoon of dough into balls. Bake for 8-10 minutes until barely golden brown. Allow to cool before transferring to a cooling rack.