Chewy Chocolate Chip Cookies

Whisk together the flour, baking soda, and cornstarch in a large mixing bowl. Set aside.

In a separate bowl, whisk the melted butter with both sugars until no lumps remain. Beat in the whole egg, followed by the egg yolk, then stir in the vanilla extract.

Pour the wet mixture into the dry ingredients and stir until a soft, thick dough forms. Fold in the chocolate chips. The dough will be quite slick.

Cover the bowl tightly and refrigerate for at least 2 hours and up to 3 days. This step is essential for thick, chewy cookies.

Allow the dough to soften at room temperature for about 10 minutes. Preheat the oven to 325 degrees Fahrenheit and line baking sheets with parchment paper. Roll the dough into balls of about 60 grams each, shaping them slightly taller than wide. Bake for 11 to 12 minutes until the edges look set but the centers still appear slightly underdone.

Let the cookies cool on the baking sheet for 10 minutes to allow them to firm up, then transfer to a wire rack to cool completely.