Preheat oven to 400 degrees F. Butter 12 muffin cups or line with paper liners.
If you haven’t already, bring the egg and sour cream to room temperature.
Stir or whisk together the flour, the baking soda, the salt, and the bran. If using spices, stir those in too.
In a large bowl with an electric mixer cream together the butter and the brown sugar until the mixture is light and fluffy, beat in the egg, the sour cream, and the molasses, and stir in the raisins.
Add flour mixture to sour cream mixture, and stir the batter until it is just combined. (The batter will be lumpy.)
Spoon the batter into muffin tins and bake the muffins in the middle of a preheated 400°F. oven for 20 minutes. If they are not done in 20 minutes, reduce heat to 350 and bake for another 3 to 5.
Turn the muffins out onto a rack and let them cool.