Preheat the oven to 350°F (175°C). Grease a baking pan (8x8 inches) or line it with parchment paper.

In a mixing bowl, whisk together the flour, baking soda, and salt.

In another bowl, cream together the softened butter, brown sugar, and granulated sugar until smooth.

Add the egg and vanilla extract to the butter mixture and mix until combined.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Fold in the chocolate chips and nuts (if using).

Spread the batter evenly in the prepared baking pan.

Bake in the preheated oven for 20-25 minutes, or until the edges are golden and a toothpick inserted in the center comes out clean.

Allow to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.

Cut into bars and serve.