Preheat the oven to 350°F (175°C). Grease a 9×13 inch baking pan or line it with parchment paper.
In a medium bowl, whisk together the all-purpose flour, baking soda, and salt. Set aside.
In a large bowl, mix the melted butter, brown sugar, and granulated sugar until well combined and smooth.
Add the egg and vanilla extract to the butter and sugar mixture and beat until fully incorporated.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Do not overmix.
Fold in the semisweet chocolate chips evenly throughout the dough.
Spread the cookie dough evenly into the prepared baking pan and smooth the top with a spatula.
Bake in the preheated oven for 22 to 25 minutes, or until the edges are golden brown and a toothpick inserted into the center comes out with a few moist crumbs.
Remove from the oven and allow to cool completely in the pan on a wire rack.
Once cooled, cut into 16 squares and serve.