Preheat your oven to 350°F (175°C). Line your baking sheets with parchment paper or silicone mats to prevent sticking.

In a medium bowl, whisk together the all-purpose flour, baking soda, and salt. Set aside.

In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar until the mixture is light and fluffy. This usually takes about 2–3 minutes using an electric mixer.

Add the eggs, one at a time, beating well after each addition. Then, mix in the vanilla extract until fully incorporated.

Gradually add the dry flour mixture to the wet ingredients, mixing until just combined. Be careful not to overmix, as this can lead to tough cookies.

Gently fold in the Belgian milk chocolate chips and toasted walnuts (if using) using a spatula or wooden spoon.

Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheets, spacing them about 2 inches apart.

Bake in the preheated oven for 15 minutes, or until the edges are golden brown and the centers have set.

Remove the cookies from the oven and let them cool on the baking sheets for 5 minutes. Then, transfer them to a wire rack to cool completely. Before serving, sprinkle a pinch of flaky sea salt on top of each cookie for an added burst of flavor.