Add 1/2 cup of the butter to a saucepan over medium heat. Melt and stir until it goes from loud and bubbly to quiet and frothy. Once it goes quiet, keep a close eye and remove the pan from the heat once the butter turns a rich amber color and gives off a nutty aroma.

Pour the brown butter into a measuring glass (scraping in the bits at the bottom of the pan) and drop 1-2 tbsp of extra butter in to make it a level 1/2 cup. Place in the fridge to cool down for about 20 minutes.

In a small bowl, whisk together the flour, baking soda, and salt. Set aside.

In a large bowl, whisk together the cooled butter (it’s ok if it’s still slightly warm), brown sugar, and sugar.

Add in the egg, vanilla and pistachio extract (if using) and whisk vigorously for about 2 minutes. The mixture should turn light in color and very smooth in consistency.

Pour in the dry ingredients and switch to a rubber spatula. Gently stir and fold the dough together and right before it’s fully mixed, toss in the chopped dark chocolate and pistachios. Continue to fold until the dough is completely combined.

Cover the bowl and chill the dough in the refrigerator for 30 minutes.

When it’s close to the 30 minute mark, preheat the oven to 350F and line a large baking sheet with parchment paper.