01 - Preheat oven to 350°F. Line two baking sheets with parchment paper and set aside.
02 - In a medium bowl, whisk together the gluten-free flour blend, baking soda, and fine sea salt until evenly distributed.
03 - In a large bowl using an electric mixer, beat the unsalted butter, walnut butter, light brown sugar, and granulated sugar on medium speed until light and fluffy, approximately 2 minutes.
04 - Beat in the egg and vanilla extract into the creamed mixture until fully incorporated and smooth.
05 - Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined. Avoid overmixing.
06 - Using a spatula, gently fold in the dark chocolate chunks and toasted walnuts until evenly distributed throughout the dough.
07 - Scoop tablespoon-sized mounds of dough onto the prepared baking sheets, spacing them approximately 2 inches apart to allow for spreading.
08 - Bake for 11 to 13 minutes, until the edges are golden and the centers appear just set. Do not overbake for optimal chewy texture.
09 - Allow cookies to rest on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely before serving or storing.