Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.
In a medium bowl, whisk together the all-purpose flour, baking soda, and salt until well combined.
In a large bowl, mix the melted and cooled butter with the light brown sugar and granulated sugar until smooth and creamy.
Add the egg, egg yolk, and vanilla extract to the butter and sugar mixture. Beat until the mixture is light and creamy, about 2 minutes.
Gradually add the dry ingredients to the wet ingredients, mixing just until combined. Do not overmix.
Fold in the semisweet chocolate chips evenly throughout the dough.
Using a tablespoon or cookie scoop, drop rounded balls of dough about 2 inches apart onto the prepared baking sheets.
Bake in the preheated oven for 10 to 12 minutes, or until the edges are golden brown but the centers still look slightly soft.
Remove the cookies from the oven and let them cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.