Preheat oven to 375°F. Line twelve 1/2-cup muffin cups with paper liners.
In a medium bowl, combine the espresso with the hot water and let it sit until the espresso dissolves. Add buttermilk, oil, eggs and vanilla and whisk until well blended.
In a large bowl, combine the flour, sugar, brown sugar, cocoa, baking powder, baking soda and salt. Add the buttermilk mixture and stir just until combined. Mix in chocolate chips.
Divide batter equally among prepared muffin cups. Bake the muffins for 20 to 25 minutes or until toothpick inserted into center of muffins comes out clean. Transfer muffins to rack and cool.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.