Preheat the oven to 350 degrees Fahrenheit. Line two baking sheets with parchment paper or a silicone liner.
Cream together the butter and sugars in a large bowl for about 3 minutes. 1/2 cup Unsalted Butter, 1/2 cup Brown Sugar, 1/4 cup Granulated Sugar
Add in the egg and vanilla and stir into the creamed butter. 1 large Egg, 1 tsp Vanilla Extract
Add the dry ingredients (flour, cornstarch, salt, baking soda, and baking powder) to the wet ingredients and stir everything together till combined, and you have a nice soft cookie dough.1 1/3 cups All Purpose Flour, 1 tsp Cornstarch , 1/2 tsp Salt, 1/2 tsp Baking Soda, 1/4 tsp Baking Powder
Add in the chocolate chips, and pistachios (reserving a few for the tops of the cookies) and stir them until mixed evenly into the batter. 3/4 cups Chopped Chocolate Bar, 1/2 cup Chopped Roasted and Salted Pistachios
Scoop the cookie dough into large 2 TBS sized cookie balls. Roll them into smooth balls.
Place cookie balls onto the prepared cookie sheet about 2-3 inches apart to allow for spread.
Bake the cookies for 10 to 12 minutes, or until the edges just start to turn golden, and the tops are barely set.
Remove the pan from the oven. Top the cookies with extra pistachio and chocolate pieces if desired. Sprinkle cookies with flakey sea salt, if desired.
Leave the cookies on the baking sheet for 5 to 10 minutes to cool, as they keep baking. Transfer the cookies to a cooling rack to cool completely, or let them cool another 5 to 10 minutes, then enjoy.