Method (5 hours):
Blend all the ingredients, except the walnuts, banana and peanut butter, in a large bowl.
Place the dough out onto a floured surface and press it into a rough square.
Sprinkle the walnuts over the surface and roll up the dough.
Knead briefly again to ensure the walnuts are thoroughly distributed throughout the dough.
Shape the dough into a ball, place in a greased bowl and cover with a tea towel.
Let the dough rise in a warm place for about 3 hours.
When it has finished rising, divide it into 2 equal parts and roll each into a ball.
Place them on a baking sheet with enough space in between to allow them to double in size.
Sprinkle plain flour and leave them uncovered for 1 hour.
Preheat the oven to 240°C. Place the bread on the bottom rack of the oven and immediately drop the temperature to 200°C.
Bake for 40 minutes.
Allow the loaves to cool before serving. Cut two slices, spread over some peanut butter and top with a sliced banana.