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, fine sea salt, and instant espresso powder until evenly distributed. Set aside.
03 - In a large bowl, beat the softened unsalted butter, hazelnut butter, packed light brown sugar, and granulated sugar using an electric mixer until the mixture is light and creamy, about 2 minutes.
04 - Add the large egg and pure vanilla extract to the creamed mixture, beating until fully incorporated and smooth.
05 - Gradually add the dry ingredient mixture to the wet ingredients, stirring gently until just combined. Avoid overmixing to maintain a tender texture.
06 - Fold the semisweet chocolate chips and chopped toasted hazelnuts into the dough until evenly distributed.
07 - Scoop tablespoon-sized portions of dough and roll into balls. Place on the prepared baking sheets, spacing about 2 inches apart to allow for spreading.
08 - Bake for 10 to 12 minutes, or until the edges are golden brown and the centers appear just set. Do not overbake.
09 - Allow the cookies to rest on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely before serving or storing.