In a large bowl combine flour, baking soda, cornstarch, and salt. Set aside.

Melt butter and place in a medium bowl. Whisk in white and brown sugar until completely dissolved. Whisk in egg and egg yolk. Stir in vanilla.

Pour butter-sugar-egg mixture over flour mixture, and gently stir until dough forms. Fold in pecans and chocolate chips. Refrigerate dough for at least 30 minutes.

Preheat oven to 325 degrees F.

Using your hands, roll dough into ¼ cup dough balls. Arrange on cookie sheet 4 inches apart. Bake until just set, about 15 minutes. Sprinkle with sea salt and let cool on cookie sheet for 5 minutes, then cool completely on a wire rack.