If you are interested in a bran muffin with a bit of extra flavor, try this sourdough bran muffin. It is packed with low-glycemic bran, and the fermentation process brings out more flavor, with just a hint of tang.
Combine starter, bran, and flour in a medium bowl. It will be a dryer dough than you would expect for muffins. Cover and place in a warm spot for 8 to 12 hours.
Once fermentation time is up, preheat oven to 425°F degrees and whisk together egg, butter, honey, salt, and spices in a small bowl. Sprinkle baking soda over fermented dough and gradually stir it in along with liquid mixture, one third at a time, adding raisins during last third. Stir just until combined.
Divide batter into 12 to 16 muffin cups and bake in pre-heated oven for about 15 minutes, or until golden brown and cooked through.