In a large bowl with a hand mixer or in the bowl of a stand mixer, cream butter, brown sugar, and sugar until light and fluffy. Add the vanilla and egg and mix until combined.
In a separate bowl, combine the flour, cornstarch, baking soda, and salt. Add the flour mixture to the butter mixture and mix until combined. Stir in the chocolate chips. Cover the cookie dough and refrigerate until firm, 1-2 hours or overnight.
Preheat oven to 350 and line a large cookie sheet with parchment paper or a silicone baking mat.
Using a medium cookie scoop, drop rounded balls of cookie dough onto the baking sheet. Bake for 5 minutes. Remove half baked cookies from the oven and press 2-3 candy corn into the top of each cookie. Return cookies to the oven and bake for another 5 minutes. Cookies will look slightly underdone and puffy.
Let the cookies sit for about 5 minutes until they setup, before moving to a cooling rack.
Notes
These cookies come out of the oven puffy, which is why it's so important to let them rest for 5 minutes before moving them to the cooling rack.