Preheat oven to 425°F. Line a muffin tin with cupcake liners.
Combine flour, cocoa powder, baking powder, salt, baking soda, and espresso powder in a large bowl, whisking to combine.
In a separate bowl whisk butter, sugar, and brown sugar until smooth. Add in eggs, one at a time, whisking to combine. Add milk, sour cream, and vanilla and whisk until smooth.
Create a well in the center of the dry ingredients; fold in wet ingredients until just combined. Fold in chocolate chips. Fill each muffin cup 3/4 of the way full with prepared batter.
Bake muffins 5 minutes at 425°F, reduce temperature to 350°F, and bake additional 12 to 14 minutes or until the tops of the muffins spring back when you press your finger into them.
Let muffins cool completely in pan before transferring to a wire rack to cool completely. Serve warm and store in an airtight container in the refrigerator 7 to 10 days.