Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone mats.
In a medium bowl, whisk together flour, baking soda, cornstarch, and salt.
In a large bowl, beat the butter, granulated sugar, and brown sugar until light and fluffy, about 2-3 minutes.
Add eggs, one at a time, beating well after each addition. Stir in vanilla.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Gently fold in the chocolate chips and nuts (if using).
Optionally, chill the dough for 30 minutes.
Using a cookie scoop or spoon, drop dough onto baking sheets, spacing them 2 inches apart.
Bake for 10-12 minutes, until the edges are golden and the centers look slightly underbaked.
Let the cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.