Preheat your oven to 350°F (175°C) and prepare a baking sheet by lining it with parchment paper.

In a medium mixing bowl, combine the softened butter with both the granulated and brown sugars. Stir for at least a minute, ensuring the ingredients are thoroughly blended. Add the egg yolk and vanilla extract, mixing until fully incorporated.

Next, sprinkle the flour, baking soda, and salt over the butter mixture. Gently fold everything together until well mixed. Stir in the chocolate chips, making sure they're evenly distributed throughout the dough.

Portion the dough into 5-6 generous mounds, each about 2 tablespoons in size, and arrange them on the prepared baking sheet, leaving enough space between each mound. If desired, press a few extra chocolate chips onto the tops of each dough ball. Shape the mounds so that they are taller rather than wider, which helps to prevent them from spreading too much during baking.

Bake the cookies for 9 to 12 minutes, or until the edges start to turn golden while the centers remain slightly soft. Once baked, remove the tray from the oven and transfer it to a wire cooling rack. Allow the cookies to cool on the baking sheet, where they will firm up as they rest.