2) Cream the butter and sugar in the bowl of an electric mixer fitted with the paddle attachment for about five minutes, until light and fluffy. With the mixer on low, add the eggs, one at a time.
3) Scrape the bowl and then add the molasses, orange zest and vanilla. (The mixture will look curdled.) Add the bran/buttermilk mixture and combine.
4) In a separate bowl, sift together the flour, baking powder, bicarbonate of soda and salt. With the mixer on low speed, slowly add the flour mixture to the batter until just combined. Don't overmix it! Using a rubber spatula, fold in the raisins, bananas and walnuts.
5) With an ice cream scoop or large spoon, fill each muffin cup liner to the top. Bake for 25 to 30 minutes, until a cake tester comes out clean.