Preheat oven to 325°F; line baking sheets with parchment.
Whisk flour, cornstarch, baking soda, and salt well in a medium bowl.
Beat butter and both sugars in a large bowl about 4 minutes, until light and fluffy.
Beat in eggs one at a time, beating well after each; mix in vanilla.
Mix flour mixture into wet ingredients on low just until combined.
Fold in chocolate chips with a spatula; chill 30 minutes.
Roll 3-tablespoon portions into tall balls; place 3 inches apart on sheets.
Bake 12-13 minutes, until edges are barely golden and centers puffy and underdone. Cool on pan 10 minutes; transfer to wire rack.