Preheat your oven to 350°F (175°C).
In a large mixing bowl, cream the room temperature salted butter, dark or light brown sugar, and granulated sugar using an electric mixer or whisk until light and fluffy, about 2-3 minutes.
Beat in the large egg and vanilla extract until well combined.
In a separate bowl, whisk together the all-purpose flour, baking soda, and flaky sea salt.
Gradually add the dry ingredients to the wet mixture, mixing just until combined. Do not overmix.
Gently fold in the coarsely chopped bittersweet or semisweet chocolate and toasted nuts, if using.
Using a cookie scoop or tablespoon, drop rounded balls of dough onto a baking sheet lined with parchment paper, spacing them apart.
Bake in the preheated oven for 10-12 minutes, or until the edges are golden brown.
Remove from oven and let cookies cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.