Preheat and prepare cookie sheets. Pre-heat oven to 325°F (160°C). Line a cookie sheet with a parchment paper or silicone baking mat.
Combine the dry ingredients. In a large mixing bowl, whisk together the flour, cornstarch, salt, baking soda, and cocoa powder.
Cream the butter and sugar. In a second bowl with an electric mixer cream together the butter and sugar until light and fluffy, about 2 to 3 minutes.
Add eggs, corn syrup and vanilla. Add the eggs one at a time, mixing well after each addition. Scrape down the sides of the bowl as needed. Beat in corn syrup and vanilla and mix well.
Add the dry ingredients. Gradually add the flour mixture to the butter mixture, beating on low speed until just combined. Stir in the chocolate chips just until combined.
Scoop the cookies. Using a 1-inch cookie scoop, or tablespoon scoop the cookies into 1 ½-inch balls onto prepared cookie sheets about 2 inches apart.
Bake and cool the cookies. Bake cookie sheet on the middle rack for 10-12 minutes, until edges are set and tops are puffy on the sides. The centers will look very soft. Remove from the oven and let cool on baking sheet for 10 minutes before transferring to a wire rack to cool completely. Cookies will be very soft.