Preheat an oven to 180 C / Gas 4. Grease 18 muffin cups, or line with paper muffin cases. Whisk the bran, flour, salt and bicarbonate of soda in a mixing bowl; set aside.
Beat the eggs in a mixing bowl. Whisk in the buttermilk, sugar, treacle and melted margarine until smooth. Stir in the bran mixture along with the raisins until no dry lumps remain. Pour into the prepared muffin tins, filling them no more than 2/3 full.
Bake in the preheated oven until a skewer inserted into the centre comes out clean, about 20 minutes. Cool in the tins for 10 minutes before removing to cool completely on a wire rack.
I didn't have any treacle but did have dark agave nectar, so substituted this. I also substituted sultanas for raisins, for the same reason. Resulting muffins had great taste and texture. I'll be making a further batch soon! - 23 Apr 2016