Preheat the oven to 200c /gas mark 6.
Sift the flour, ground cinnamon, baking powder, bicarbonate of soda, fudge chunks, salt and sugar into a large mixing bowl.
In a small bowl or jug, stir the egg, oil, mashed banana and vanilla extract.
Fold the banana mixture into the dry ingredients until just combined. Do not over mix.
Spoon the batter evenly into the paper cases. Top each one with a light sprinkle of demerara sugar. Bake the muffins for 15 minutes.?
Allow the muffins to cool in the tray for a few minutes before transferring to a wire cooling rack.