Combine the dry ingredients in the bowl of a free-standing electric mixer fitted with a dough hook.
Add all the remaining ingredients apart from the egg, with 250ml/9fl oz tepid water and begin kneading on a slow speed. Add up to 100ml/3½fl oz more water a little at a time to make a soft, but not wet dough.
Knead on a slow speed for approximately two minutes, then increase the speed and knead for four minutes on a medium speed.
Turn the dough out onto a lightly floured work surface and knead by hand, breaking any large walnut pieces that remain, until the dough is smooth and pliable. Set aside in a large, lightly oiled bowl, covered with a tea towel to prove for approximately one hour, or until the dough has doubled in volume.
Knock back the dough and separate 200g/7oz off from the rest. Set aside, covered while you shape the loaf.
Form the larger portion of the dough into a smooth cob flattened slightly into a circle approximately 30cm/12in in diameter and place onto the lined baking tray.
Place a 7.5cm/3in round cutter in the middle of the dough. Cut the dough around the periphery using a knife to create 16 segments (petals).
Twist each petal 90 degrees. Cut out the circle of dough from the centre and shape into a ball. Set aside, covered with a tea towel.
Divide the reserved 200g/7oz of bread dough into two balls. Roll these out thinly into circles. Divide each circle into eight triangles. Place the short ends of each triangle within the central hole and fold back the points into the centre to create inner petals of the flower.
Place the reserved ball of dough back in the centre of the flower. Cover with oiled cling film and prove again until the dough has doubled in size.
Preheat the oven to 210C/fan oven 190C/Gas 7 and line a baking tray with baking parchment
Brush the inner petals with the beaten egg and dust the outer petals with a little white flour
Using the tip of a sharp knife cut the central boule to mimic the appearance of the centre of a flower.
Bake for 30-35 minutes until the loaf sounds hollow when the base is tapped.