Preheat your oven to 350°F (175°C) to ensure even baking.
Melt the 3 tablespoons of butter in a mixing bowl.
Stir in the light brown sugar and granulated sugar until well combined.
Add the egg yolk and whisk until smooth for a rich texture.
If using, mix in the vanilla extract for extra flavor.
Sprinkle in the baking soda, corn starch, and flour over the wet ingredients and mix until just combined.
Fold in the chocolate chips until evenly distributed.
Scoop the dough onto a baking sheet and shape it into a cookie form, about 1/2 inch thick.
Bake for about 10-12 minutes, until the edges are golden but the center is still soft.
If using, sprinkle flaky sea salt on top as soon as it comes out of the oven.
Cool for a few minutes on the baking sheet before transferring to a wire rack. Enjoy!
