60% Cacao dark chocolate. Natural source of flavanol antioxidants. The natural antioxidants found in tea and certain fruits like berries and grapes can also be found in Hershey's Extra Dark. This is good news; however, like most indulgent treats, Hershey's Extra Dark should be enjoyed in moderation. A serving of Hershey's Extra Dark Pure Dark Chocolate is 3 blocks (37 g) and has 210 calories and 13 g of fat. Total calories per bar 550.