1Heat oven to 400ºF. Grease bottoms only of 12 regular-size muffin cups (2 1/2x1 1/4 inch) with shortening, or line muffin cups with paper baking cups.
2In medium bowl, mix flour, cocoa, baking powder and salt; set aside. In large bowl, beat brown sugar, milk, oil, coffee and egg with fork or wire whisk. Stir in flour mixture just until flour is moistened. Fold in chocolate chunks. Divide batter evenly among muffin cups.
3Bake 18 to 20 minutes or until toothpick inserted in center comes out clean. Immediately remove from pan.