If you want to toast your pistachios before adding them to the batter, place them on a rimmed baking sheet and bake them at 350°F (180°C) until fragrant and beginning to turn golden, 8 to 10 minutes. If your nuts have any skins on them, you can remove them by gathering the warm toasted nuts in a kitchen towel and rubbing them together. The skins should fall off easily. Remember to let the toasted pistachios cool completely before adding them to the cookie dough.