Preheat the oven to 350°.
Using a stand mixer, cream together the butter and sugars until light in color and fluffy in texture.
Add in the eggs, corn syrup and 1 tbsp of vanilla. Mix until thoroughly combined.
Next, add the flour, cocoa, cornstarch baking soda and salt. Mix until your chocolate cookie dough forms. The dough will be soft.
Divide the dough out into 12 equal portions, I like to use my 1/2 cup measuring cup to help divide the dough. You'll want to use a little less than 1/2 cup of dough to have 12 cookies.
Roll the cookie dough into a ball and then use your thumb to create a pocket in the middle of the cookie dough.
Spoon approx 1/2 tbsp of hot fudge into each pocket and then close the cookie dough around the hot fudge.
Slightly flatten the cookie so the cookie looks like a hockey puck.
Repeat with remaining cookie dough. Place 6 cookies per tray.
Bake at 350° for 15-17 minutes. The cookie should start to crack and crinkle, it will spread slightly and the centers of the cookie should no longer look wet before taking them out of the oven.
Allow the cookies to cool on the pan for about 15 minutes.
Dust with powdered sugar and serve warm.