Preheat oven to 375°F and line a cookie sheet with parchment paper.
In a food processor or blender, grind the pistachios until finely chopped to the texture of coarse sand. Do not grind to the point where the pistachios start releasing oil. Set aside.
In a large bowl, combine butter and sugars together until smooth.
Add the egg and vanilla extract and mix until smooth.
Add the flour, baking soda, salt and ground pistachios and mix until just combined.
Add the chopped pistachios and white chocolate chunks.
Scoop 1.5 tbsp cookies and transfer to the prepared baking sheet. Leave at least 2 inches (5 cm) between each cookie.
Bake for 8-10 minutes or until the center goes from being wet and shiny to being matte. The bottom of the cookies will be lightly golden brown. Let cool on the cookie sheet or a wire rack.