Preheat oven to 350°F. Prepare 2 cookie sheets with parchment paper.
Place butter in a small, light colored saucepan and set oven medium-low heat. Stirring or swirling constantly, brown the butter until you smell a nutty aroma and see light brown flecks appear. Butter will crackle and froth as it toasts, continue to stir. Remove from the heat once brown flecks appear and pour into a large mixing bowl. Set aside to cool, about 10 minutes.
170 g unsalted butter
While browning butter, place pistachios in a pan and toast for 10 minutes, until they are fragrant. Coarsely chop and set aside.
100 g pistachios, roasted and salted, unshelled
In a separate bowl, whisk together flour, baking powder, baking soda and salt.
300 g all-purpose flour, 1 teaspoon baking powder, 1/2 teaspoon baking soda, 1/2 teaspoon salt
Once butter is cool to the touch, whisk in both sugars. Then add eggs and vanilla.
159 g light brown sugar, 50 g granulated sugar, 2 large eggs, 1 teaspoon vanilla extract
Stir in flour mixture using a rubber spatula, then chopped pistachios and white chocolate.
170 g chopped white chocolate or chips
Using an ice cream scoop, scoop 15 cookies. Roll the scoops slightly in your hands then flatten into a disc shape on 3 baking sheets topped with parchment paper.
Bake 17-19 minutes at 350°F, until edges are lightly browned and the center is soft.
Wait 5 minutes before transferring to a cooling rack.