The Best Bran Muffins

Name: The Best Bran Muffins
Ingredients: 1 1/4 cups bleached all-purpose flour; 1/4 cup whole-wheat flour; 1 1/4 teaspoons baking powder; 1/2 teaspoon baking soda; 3/4 teaspoon table salt; 1 1/4 teaspoons ground cinnamon; 3/4 teaspoon ground allspice; 1/2 teaspoon fresh grated nutmeg; 7 tablespoons unsalted butter , softened; 1/2 cup dark brown sugar plus 2 additional tablespoons; 2 large eggs; 2 1/2 teaspoons vanilla extract; 3 tablespoons unsulphured molasses; 1/4 cup sour cream; 1 cup buttermilk plus 3 additional tablespoons; 1 1/2 cups wheat bran; 1 cup raisins