1-Combine Dry Ingredients: Whisk flour, baking soda, cornstarch, and salt together in a large bowl.

2-Combine Wet Ingredients: In a medium bowl, whisk melted butter, brown sugar, and granulated sugar until smooth. Whisk in the whole egg and egg yolk, then whisk in the vanilla extract.

3-Mix Dough: Pour the wet ingredients into the dry ingredients. Mix gently with a spoon or spatula until just combined. Fold in the chocolate chips.

4-Chill Dough: Cover the dough tightly and refrigerate for at least 2 hours, or up to 3 days to ensure thickness.

5-Preheat Oven & Prepare: Preheat oven to 325°F (163°C). Line baking sheets with parchment paper or silicone mats.

6-Temper Dough (if needed): If chilled longer than 2 hours, let the dough sit at room temperature for 15 minutes before scooping.

7-Shape Dough: Scoop dough into balls. Use about 3 scant tablespoons for extra-large cookies or 2 heaping tablespoons for medium-large. Shape balls to be tall and lumpy.

8-Arrange Dough: Place dough balls 3 inches apart on the prepared baking sheets.

9-Bake: Bake for 13 14 minutes, until the edges are lightly browned but the centers remain soft.

10-Cool: Cool cookies on the baking sheet for 10 minutes. Then, transfer to a wire rack to cool completely. Optionally, press extra chocolate chips onto the tops while warm.

11-Store: Store cooled cookies in an airtight container at room temperature for up to 1 week.