Lightly spray the top surface of a muffin tin. Line 10 holes of the muffin tin with muffin liners/wrappers.
In a medium sized bowl, cream together the butter and sugar with an electric hand mixer until light and fluffy.
Beat in the egg, buttermilk, vanilla, mashed banana and molasses. At this point the mixture might look a bit curdled and messy, it’s completely normal. Stir in the raisins.
Get a separate, large bowl. Sift together flour, baking powder, bicarbonate of soda, cocoa powder, spices and salt. Stir in the bran.
Make a well in the center of your dry ingredients. Pour the wet mixture into the well. Stir the batter with a metal spoon until it is just combined (the batter will be slightly lumpy.)
Divide the batter evenly into the 10 lined muffin holes. Sprinkle with regular, rolled oats.
Bake the muffins in the middle of the oven for 20 - 25 minutes, or until a skewer tests clean. Leave to cool in the muffin tin for 10 minutes.
Place the muffins on a rack and let them cool further, or eat them :)
Recipe by Philosophy Of Yum Blog at https://philosophyofyum.com/ultimate-bran-muffins/