Preheat oven to 375 degrees. Combine butter, sugars, and corn syrup in a bowl with electric mixer. Beat in eggs, one at a time. Stir in vanilla.
In separate bowl, combine flour, baking soda, and salt. Add dry ingredients to the creamy mixture. Do not overbeat.
Fold in chopped chocolate.
Roll out dough into 2-inch balls and place on cookie sheet. Bake until the cookies are set on the edges and gooey in the center, about 8 minutes. Let cool for 5 minutes.