Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a stand mixer fitted with the paddle attachment, cream together butter, brown sugar, granulated sugar, and salt on medium-low speed until smooth and well-combined, about 4 minutes.
3/4 cup butter, 1 cup brown sugar, 1/3 cup granulated sugar, 1 1/2 tsp salt
Add in the eggs, egg yolk, and vanilla extract. Beat on low speed for an additional 2 minutes.
2 eggs, 1 egg yolk, 2 tsp vanilla extract
Gradually sift in the flour and baking soda. Mix until just combined, ensuring not to overmix.
2 1/3 cup flour, 1 tsp baking soda
Fold in the chopped white chocolate and pistachios until evenly distributed in the dough.
10.5 oz white chocolate, 4 oz shelled roasted pistachios
Using a scoop, portion out the cookie dough into 1.5 oz portions and place them on the prepared baking sheet, spacing them adequately apart (8 cookies per sheet).
Bake in the preheated oven for 10 minutes or until edges are lightly golden. Once out of the oven, while cookies are still hot, you can press additional pistachio pieces and white chocolate chunks into the top of each cookie for a decorative touch. (optional)
Allow cookies to cool on the baking sheet for about 5 minutes, then transfer them to a wire rack to cool completely.