Slightly adapted from epicurious.com
1/2 cup raisins
1 tablespoon dark rum
1 stick unsalted butter, softened
1/4 cup firmly packed light brown sugar
1 extra-large egg, beaten lightly
1 cup sour cream
1/4 cup dark molasses
1 cup all-purpose flour
1 teaspoon baking soda
1/4 teaspoon salt
1 cup all bran
Preheat oven to 400°F.
Measure out raisins and place them in a small bowl. Pour rum over raisins, oppressing down on raisins to cover and set aside while you make the muffin batter.
In a large bowl with an electric mixer cream together the butter and brown sugar until the mixture is light and fluffy. Beat in the egg, sour cream, and molasses, and stir in the raisin/rum mixture.
In a separate bowl whisk together the flour, baking soda, salt, and bran. Add the dry mixture to the sour cream mixture, and stir the batter until it is just combined. (The batter may be lumpy.) Spoon the batter into 12 well-buttered 1/3-cup muffin tins (or use paper liners) and bake the muffins in the middle of the oven for 15 to 20 minutes, or until they are golden brown and springy to the touch. Turn the muffins out onto a rack and let them cool.
http://pattietierney.blogspot.com/2016/02/sour-cream-bran-muffins.html