For best results, use a kitchen scale to weigh the ingredients.
Instructions
Make the caramelized pistachios. Add pistachios to a saucepan or shallow frying pan. Sprinkle in sugar and cook over medium high heat stirring frequently until it smells fragrant nutty and the sugar melts and caramelizes. It will be dark brown. Turn it out onto a piece of parchment on a baking tray and immediately sprinkle with salt. Set it aside to cool and harden, then coarsely chop into pieces.
Make the cookie dough.Brown the butter. Follow the instructions in this post here to learn how to brown butter. t’s easy! Brown specks and a dense golden foam will form at the surface when it is nearly ready. Pour it out into a clean bowl and let it cool for 10 minutes. This whole process takes around 8-10 minutes. Immediately pour it into a large mixing bowl, then let it cool for 20-30 minutes until it reaches a temperature just warmer than room temperature. If you care to measure, the butter should read 34°C or 93°F on a digital thermometer. It should not be hot, but it should not be too cool or it will stiffen up when you mix in the other ingredients if it is cold in your kitchen.
Combine flour, baking soda, baking powder and salt in a medium bowl and whisk well to blend evenly.
Combine cooled brown butter with both sugars in a large bowl and mix gently to combine. It should look thick like wet sand. You can also mix it in the bowl of a stand mixer fitted with the paddle attachment on medium speed for 30 seconds.
Add the egg, milk and vanilla and mix it in until well incorporated and creamy-looking. Do not mix vigorously at this stage because if it is cold in your house, the butterfat will firm up and become stiff.
Add flour mixture and fold it in or mix on low just until mostly combined, but before all of the flour is absorbed add the white chocolate chips and chopped caramelized pistachios and continue mixing until they are evenly distributed. Cover the bowl and refrigerate the dough for 30 minutes while you preheat the oven.
Use a 1.35-oz cookie scoop to portion dough into 14 or 15 portions and roll into smooth balls. Place them onto prepared baking sheets, spacing them 3 inches apart. Flatten slightly and bake for 8-10 minutes until golden on top, browned around the edges and soft in the middle.
Let cookies cool on baking sheet for 2 minutes before carefully transferring to a wire rack to finish cooling.