Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.

Whisk together the flour, baking soda, and salt in a bowl.

Cream the butter with granulated sugar and brown sugar in a mixing bowl until light and fluffy, about 2-3 minutes.

Add the egg and vanilla extract to the butter mixture, mixing until fully combined.

Gradually mix in the dry ingredients to the wet mixture, stirring just until combined.

Fold in the chopped pistachios and dark chocolate chunks until evenly distributed.

Scoop tablespoon-sized portions of the dough onto the prepared baking sheet, spacing them about 2 inches apart.

Sprinkle sea salt flakes on top of each cookie for a delightful sweet and salty contrast, if desired.

Bake for 10-12 minutes, or until the edges are golden brown but the centers look slightly underbaked.

Cool on the baking sheet for 5 minutes and then transfer to a wire rack to cool completely.