Preheat the oven to 350°F (180°C). Line a 9x13-inch baking pan with parchment paper or foil, making sure to leave some overhang for easy removal, and set aside.
In a large mixing bowl, whisk together the melted butter and brown sugar until fully combined, then whisk in the eggs, egg yolk, and vanilla extract until just combined.
Add the flour, baking soda, and salt and mix until just combined, then fold in the semi-sweet chocolate chips.
Scoop the batter into the prepared baking pan and spread it out into one even layer.
Bake for about 25 minutes or until the tops of the bars are set and lightly browned.
Remove from the oven and transfer to a wire rack to cool completely. Once cooled, lift the bars out of the pan using the overhang from the foil or parchment paper, slice into bars, serve, and enjoy!