Preheat your oven to 350°F (175°C). Grease an 8x8-inch baking pan and line it with parchment paper, leaving some overhang for easy removal.
In a saucepan over medium heat, melt the butter. Cook, swirling the pan occasionally, until the butter turns golden brown and develops a nutty aroma, about 5-7 minutes. Remove from heat and let it cool slightly.
In a large mixing bowl, combine the brown sugar and granulated sugar. Pour the slightly cooled brown butter over the sugars and mix until well combined.
Add the egg and vanilla extract, mixing well until fully incorporated.
In a separate bowl, whisk together the flour, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Be careful not to overmix. Fold in the chocolate chips.
Transfer the cookie dough to the prepared baking pan and spread it out evenly using a spatula
Place the pan in the preheated oven and bake for 20-25 minutes, or until the edges are golden brown and a toothpick inserted into the center comes out clean or with a few moist crumbs.
Allow the cookie bars to cool completely in the pan on a wire rack. Once cooled, use the parchment paper overhang to lift the bars out of the pan and transfer them to a cutting board. Slice into bars and serve.
