Start by preheating your oven to 350ºF (180ºC). Prepare two baking sheets by lining them with parchment paper or silicone baking mats. This will ensure your cookies don’t stick and bake evenly.
In a large bowl or the bowl of a stand mixer, combine salted butter, brown sugar, and granulated sugar. Beat the mixture on medium speed until smooth and creamy. You want this to be light and fluffy, which should take about two to three minutes.
Once your butter and sugars are well combined, add in a large egg and a splash of vanilla extract. Beat again until everything is fully incorporated. You’re looking for a rich, creamy batter.
In a separate small bowl, whisk together the dry ingredients: flour, baking soda, and flaky sea salt. This step ensures that your leavening agent is evenly dispersed throughout the dough.
Now it’s time to combine the wet and dry ingredients. Gradually stir the dry mixture into the butter mixture. Mix until just combined. Avoid overmixing, as it can lead to tough cookies.
Fold in the chocolate chunks and toasted nuts (if using) with a spatula. Be generous with the chocolate; you want every bite to be filled with melty goodness!
Cover the bowl with plastic wrap and chill the cookie dough in the refrigerator for at least one hour. For best results, chill it overnight. This step is crucial for flavor development and achieving the perfect texture.
Once the dough is chilled, scoop out portions about the size of a large unshelled walnut and form them into rounds. Place them on the prepared baking sheets, spacing them about two inches apart. Press down the tops gently to flatten them slightly.
Bake the cookies for about ten minutes. Keep an eye on them; they should be set but not browned. Rotate the baking sheets halfway through to ensure even baking.
After baking, remove the cookies from the oven. Using a spatula, gently tap the tops of each cookie for an even texture, then return them to the oven for an additional two to five minutes until golden brown.
Finally, let the cookies cool on the baking sheets before transferring them to a wire rack. This allows them to firm up and makes them easier to handle.