14 teaspoons chocolate-hazelnut spread (such as Nutella®)
Instructions
Preheat the oven to 400 degrees F (200 degrees C). Line 14 muffin cups with paper liners and set aside.
Combine sugar and butter in a large bowl; beat until creamy. Dissolve espresso powder in hot water. Add to the butter mixture along with the yogurt, eggs, and vanilla. Mix well.
Whisk flour, cocoa powder, baking powder, and salt together. Fold into the wet ingredients just until combined. Do not overmix.
Divide 1/2 of the batter evenly among the prepared muffin cups, filling only halfway. Drop a heaping teaspoon of chocolate-hazelnut spread in the center of each. Top with the remaining batter.
Bake in the preheated oven until the center springs back lightly touched with your finger, 15 to 18 minutes. Cool for 10 minutes in the pan before transferring muffins to a cooling rack to cool completely.