In a large bowl, cream butter and sugars until light and fluffy. Add the eggs, one at a time, beating well after each addition. Beat in corn syrup and vanilla. Combine the flour, cocoa, baking soda and salt; gradually add to the creamed mixture and mix well. Stir in chocolate chips.
Roll into 1-1/2-in. balls; roll in sugar if desired. Place 2 in. apart on ungreased baking sheets. Bake at 350° for 12-14 minutes or until cracks look dry. Cool for 2 minutes before removing to wire racks.