Preheat the oven to 350°F. Line two standard 12-cup muffin pans with paper or silicone muffin cups, and grease the cups., In a large mixing bowl, whisk together the cocoa, flour, sugar, baking powder, espresso powder, baking soda, salt, Cake Enhancer, and chocolate chips. Set aside., In a large measuring cup or medium-sized mixing bowl, whisk together the eggs, milk, vanilla, oil, and vinegar. Stir this mixture into the dry ingredients, mixing until everything is well combined., Spoon the batter into the prepared muffin pans, filling the cups about 3/4 full., Bake the cupcakes for 20 to 22 minutes, or until a cake tester or toothpick inserted in the center of one of the middle cupcakes comes out clean., Remove the cupcakes from the oven, and as soon as you can handle them, remove them from the pan, and transfer to a rack to cool. Store cooled cupcakes airtight.