Preheat oven to 350 degrees F. Add the butter, sugar and brown sugar to the bowl of a stand mixer. Mix on low until combined and then beat on medium speed for about 1 minute. Beat in the egg, vanilla extracts until light and fluffy.
In a separate clean bowl, whisk together the dry ingredients - flour, baking powder, baking soda and salt.
Stop the mixer and add the flour mixture, dark chocolate chips and pistachios. Mix on low speed until a cohesive cookie dough forms, about 1 minute.
Use a medium size cookie scoop (about 1 1/2 tablespoons capacity) to form 24 cookie dough balls. Place the cookies evenly spaced on baking sheets lined with Silpat baking mats or parchment paper (12 cookies per baking sheet).
Bake the cookies for 10 - 12 minutes. I rotate the pans front to back and top rack to bottom rack halfway through baking time.
The cookies should look a bit underdone when you take them out of the oven. They will set up as they cool.
Allow the cookies to cool on the baking sheets for 10 minutes, or until they've firmed up. Remove to a cooling rack and allow them to cool to room temperature.
Cookies are best eaten within a day or two. If you'd like to freeze the cookies, layer them into an airtight container, separating the layers by sheets of wax paper. They will stay fresh in the freezer for up to one month.