Preheat your oven to 350°F/180°C and line two baking sheets with parchment paper.
In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy. This should take about 3-4 minutes with an electric mixer.
Beat in the egg, followed by the vanilla extract, ensuring everything is well combined.
Sift in the flour, baking soda, and salt. Mixing until just combined.
Gently fold in the chocolate chunks and chopped walnuts, ensuring they're evenly distributed throughout the dough.
Cover the bowl with a plastic wrap. Refrigerate for 1 hour.
Using a cookie scoop or tablespoon, dip the rounded balls of dough into chocolate chips then place them onto the prepared baking sheets, spacing them about 2 inches apart.
Bake the cookies for 9-10 minutes, or until the edges are golden brown but the centers are still soft. Remember, they will continue to cook on the baking sheet after you remove them from the oven.
Allow the cookies to cool on the baking sheet itself.
