Remove pips from the orange and finely chop with skin on then place in a kitchen whizz and add orange juice, egg, oil and dates. Pulse briefly. Tip into large bowl and gently fold dry ingredients in orange mixture except for the brown sugar and walnuts. Spoon into greased muffin pan and sprinkle over the top the combined brown sugar and walnuts. Bake 15 minutes @ 200c. Cool briefly in pan and tip on to wire rack to cool further. Walnuts can be substituted by mixing cinnamon and brown sugar together and sprinklinge on top before baking.