1.Preheat oven to 160°C. Grease 14cm x 23cm (5½-inch x 9¼-inch) loaf pan; line base and sides with baking paper.
2.Melt butter; cool. Lightly beat eggs in large bowl, stir in butter, mashed banana, sugar, buttermilk and treacle. Stir in choc bits, sultanas, prunes and half the nuts; stir in sifted flours, soda and spices.
3.Spread mixture into pan; cover pan with greased pleated foil. Bake 1 hour.
4.Meanwhile, slice banana thinly on an angle. Remove foil from loaf; top loaf with banana, sprinkle with remaining nuts. Bake loaf about 1½ hours. Stand loaf in pan 10 minutes, before turning, top-side up, onto wire rack to cool.
You will need about 3 large overripe bananas for this recipe; mash 2 of them for enough mashed banana.