Preheat the oven to 375°F (190°C). Line a baking sheet with parchment paper.
In a large mixing bowl, cream together softened butter, brown sugar, and granulated sugar until fluffy.
Add eggs and vanilla extract. Mix until well combined.
In a separate bowl, whisk together flour, cornstarch, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the chocolate chips evenly.
Scoop dough into large balls (about 1/3 cup each) and place on the prepared baking sheet.
Gently flatten each dough ball and bake for 12–14 minutes, until edges are golden but centers remain soft.
Cool on the baking sheet for 10 minutes before transferring to a wire rack.