PREPARATION:

1. Preheat oven to 400°F. Lightly grease 12 standard (2-1/2-inch) muffin cups or line with paper baking cups.
2. Combine flour, granulated sugar, cocoa, baking soda and salt in large bowl. Combine buttermilk, egg, butter, coffee mixture and vanilla in medium bowl; beat until blended. Stir buttermilk mixture into flour mixture just until dry ingredients are moistened. Stir in macadamia nuts. Spoon batter evenly into prepared muffin cups.
3. Bake 13 to 17 minutes or until toothpick inserted into centers comes out clean. Cool in pan on wire rack 5 minutes. Remove from pan to wire rack; cool 10 minutes. Sprinkle with powdered sugar, if desired.