Chocolate Walnut Muffins with Espresso

Steps

1. Heat the oven to 375°F (190°C) and line a 12-cup muffin pan with paper liners.
2. Toast the walnuts on a baking sheet in the oven for 6 to 8 minutes until fragrant, let cool, then chop. Set aside one quarter of the walnuts for the topping; the remaining three quarters go into the batter.
3. Melt the butter and let it cool slightly.
4. In a small bowl, whisk the unsweetened cocoa powder into the hot espresso until smooth to bloom it for deeper chocolate flavor. Let the cocoa-espresso mixture cool for 5 minutes.
5. In a large bowl, whisk together the flour, brown sugar, baking powder, baking soda and salt.
6. In a medium bowl, whisk the eggs, yogurt, melted butter and vanilla, then whisk in the cocoa-espresso mixture.
7. Pour the wet mixture into the flour mixture and fold with a spatula until just a few streaks of flour remain.
8. Fold in the chocolate chips and the three quarters of the walnuts set aside for the batter until just combined; do not overmix.
9. Divide the batter evenly among the 12 muffin cups.
10. In a small bowl, toss the remaining quarter of the walnuts with the granulated sugar, then sprinkle this walnut-sugar topping over the muffins.
11. Bake for 18 to 22 minutes, until a toothpick inserted in the center comes out clean apart from melted chocolate.
12. Cool in the pan for 5 minutes, then move the muffins to a rack to cool for at least 15 minutes before serving.