Mix bran, buttermilk, molasses and brown sugar in a small bowl, let stand until all liquid is absorbed.
Sift flour, baking powder, baking soda and salt into large bowl. Stir in raisins, if desired.
Stir egg and melted shortening into bran mixture. Add bran-egg mixture all at once into flour mixture. Stir lightly with a fork until evenly moist.
Spoon batter into heat-resistant plastic coffee cup holders that have been lined with paper muffin liners. Fill muffin cups 1/2 full.
Place 6 muffins at a time around the outside edge of the turn- table, leaving the center of the turntable empty. Heat, uncovered, in Microwave Oven 3 minutes, or until muffins test done with a toothpick.
Repeat with remaining muffin batter.
Makes 12 muffins