Prep time 15 minutes
Cook time 15 minutes
Yield: Serves or Makes 12
Preheat oven to 425°F and line a 12-cup standard muffin pan with baking cups; spray baking cups lightly with cooking spray. Dissolve espresso in boiling water, and set aside to cool to room temperature. Whisk together flour, cocoa, sugar, baking powder, baking soda, and salt in a large bowl; make a well in the center of the mixture. Combine buttermilk, yogurt, melted butter, egg, vanilla, and cooled espresso in a medium bowl; add to flour mixture and fold in until almost combined. Add melted chocolate and fold in gently; fold in chocolate chips.
Fill each baking cup 3/4 full of batter and sprinkle with chocolate chips. Place muffin pan in the oven and bake for 5 minutes at 425°F. Reduce temperature to 350°F and continue baking 9 to 11 minutes (for a total baking time of 14 to 15 minutes), until muffins are set and a toothpick inserted in the center comes out clean or with a few crumbs attached. Let muffins cool in pan on a wire rack for 5 minutes before removing from pan to cool. Dust with powdered sugar.