Preheat Oven: Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper or a silicone baking mat.
Mix Dry Ingredients: In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.
Cream Butters and Sugar: In the bowl of a stand mixer fitted with the paddle attachment, beat the softened butter, pistachio butter, brown sugar, and granulated sugar together on medium speed until light and fluffy, about 2–3 minutes.
Add Egg and Vanilla: Beat in the egg and vanilla extract until fully incorporated.
Incorporate Dry Ingredients: Gradually add the dry ingredients to the butter mixture, mixing on low speed until just combined.
Add Toffee and Pistachios: Gently fold in the chopped toffee and pistachios until evenly distributed throughout the dough.
Shape Cookies: Using a cookie scoop or tablespoon, drop dough onto the prepared baking sheet, spacing the cookies about 2 inches apart.
Bake: Bake for 10–12 minutes, or until the edges are lightly golden and the centers are just set. Be careful not to overbake, as the cookies will continue to firm up as they cool.
Garnish: Sprinkle with flaky salt (optional but recommended)
Cool and Serve: Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
Enjoy your chewy, buttery Pistachio Toffee Cookies with their perfect balance of nutty and sweet flavors!