1. Preheat oven to 350-375°F and line a baking sheet with parchment paper.
2. In a bowl, whisk together flour, baking soda, salt, and cornstarch if using.
3. In a separate bowl, cream softened or melted and slightly cooled butter with brown sugar and white sugar until fluffy.
4. Add eggs and vanilla extract to the butter mixture and mix until combined.
5. Gradually mix in the dry ingredients until just combined, being careful not to overmix.
6. Fold in chocolate chips gently.
7. Chill the dough for at least 30 minutes, up to 36 hours for enhanced flavor.
8. Use a cookie scoop to portion the dough and shape into taller balls for thicker cookies.
9. Place dough balls on the prepared baking sheet, spacing them apart.
10. Bake for 8-12 minutes until edges are lightly golden but centers are still soft.
11. Remove from oven and let cookies cool on the baking sheet for 5-10 minutes.
12. While still warm, add extra chocolate chips on top for a better appearance.
13. Transfer cookies to a cooling rack to cool completely.
14. Store cookies in an airtight container at room temperature for up to one week.
15. Optionally, freeze extra dough balls to bake fresh cookies later.