Preheat oven to 375 degrees F.
Whisk together flour, baking soda, cornstarch, and salt.
In a stand mixer on medium speed, or with a hand mixer, cream together butter, sugar, and molasses for 2-3 minutes until lightened in color.
Beat in the eggs, one at a time, and vanilla, scraping the bowl down, until well combined.
Reduce the speed to low and add flour mixture, mixing until just combined. Stir in the chocolate chunks.
Scoop 3 tablespoons of dough shaped into a rough ball, 2 inches apart onto lined cookie sheets. Bake until the cookies are golden brown and just set in the center, 12 to 15 minutes.
Cool for 5 minutes on the baking sheets and transfer to wire racks to cool completely. Store in an airtight container for up to 5 days.