Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.
In a large bowl, cream together the softened butter, granulated sugar, brown sugar, and miso paste until smooth and well combined.
Beat in the egg and vanilla extract until fully incorporated.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the black sesame seeds and chocolate chips, if using.
Scoop tablespoon-sized portions of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake for 10-12 minutes, or until the edges are lightly golden.
Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.