Preheat oven to 350 degrees F. Line a large baking sheet with a Silpat baking mat or parchment paper and set aside.

In a large bowl, whisk together flour, salt, baking powder, and baking soda. Set aside.

Using a mixer, cream butter and sugars together until light and fluffy, about 3 minutes. Add the egg and vanilla and beat for an additional 2 minutes.

With the mixer on low, slowly add in the dry ingredients. Mix until just incorporated.

Stir in the pistachios and chocolate chunks. Using a spoon or cookie scoop, form tablespoons size balls of cookie dough. Place balls on prepared baking sheet, about 2 inches apart. Sprinkle cookie dough balls with sea salt. Bake cookies for 12 minutes, or until lightly browned around the edges. Let cookies sit on baking sheet for 2 minutes. Transfer cookies to a wire cooling rack and cool completely. Store in an air-tight container for up to 4 days.