1Whisk together flour, baking powder, baking soda, and cornstarch in a medium bowl. Set aside.
2Cream together brown sugar, granulated sugar, and butter in a large bowl until light and fluffy.
3Beat in eggs one at a time, followed by vanilla extract, for 3-4 minutes until the batter turns pale and the sugar is well incorporated.
4Gradually mix in dry ingredients until just combined, being careful not to overmix.
5Stir in chocolate chips.
6Scoop 2 tablespoon-sized balls of dough onto the prepared baking sheet. Leave the dough balls slightly rough and stacked, with a rustic texture. Place 4 cookies on each pan, leaving 4 inches of space between each one. Top with extra chocolate chips.
7Bake for 13-16 minutes on middle rack or until edges are lightly golden brown.
8Remove from oven and let cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.