1-First, whisk the flour, baking soda, cornstarch, and salt in a large bowl until they’re well combined. This step ensures your dry ingredients mix evenly, which helps the cookies rise and stay soft.

2-Next, in another bowl, whisk the melted butter with both sugars until the mixture is smooth and creamy.

3-Then, add the egg and egg yolk, followed by the vanilla extract, and mix everything until it’s fully incorporated. This brings in moisture and richness that makes the cookies extra chewy.

4-Now, combine the wet and dry ingredients by folding them together gently, and stir in the chocolate chips to distribute them evenly.

5-After that, chill the dough for at least 2 hours or up to 3 days to prevent spreading and achieve that bakery-style texture.

6-Once chilled, preheat your oven to 325°F (163°C) and line your baking sheets with parchment paper. Scoop the dough into tall, lumpy balls and place them on the sheets.

7-Bake for 13 to 14 minutes until the edges are lightly browned, then let the cookies cool on the sheet for 10 minutes before transferring to a rack.